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October 2013

HEALTH TECHNICAL MEMORANDUM 2030

Washer disinfectors: Design considerations

1997

STATUS IN WALES

ARCHIVED

This document was superseded by

Welsh Health Technical Memorandum 01-01 Decontamination of medical devices within acute

services

2013

Washer-disinfectors

Design considerations

Health Technical Memorandum 2030

London: The Stationery Office

© Crown copyright 1997. Published with permission of NHS Estates, an Executive Agency of the Department of Health, on behalf of the Controller of Her Majesty’s Stationery Office.

Applications for reproduction should be made in writing to The Copyright Unit, Her Majesty’s Stationery Office, St Clements House, 2–16 Colegate, Norwich NR3 1BQ.

First published 1997

ISBN 0-11-322069-3

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Health Technical Memoranda (HTMs)

give comprehensive advice and

guidance on the design, installation and

operation of specialised building and

engineering technology used for the

delivery of healthcare.

They are applicable to new and existing

sites, and are for use at various stages

during the inception, design,

construction, refurbishment and

maintenance of a building.

Health Technical Memorandum 2030 is

being published in three volumes.

Operational management is a

summary of the information required by

personnel responsible for the

management of facilities in which

washer-disinfectors are used. It discusses

the various types of washer-disinfectors,

for both clinical and laboratory use, and

also contains guidance on legal and

policy matters, and on the appointment

and responsibilities of personnel. It

covers all aspects of routine operation

and maintenance stressing the need for

a planned maintenance programme

along with the type of records to be

kept. Advice on the safe and efficient

operation of washer-disinfectors is

given, as well as procedures for

reporting defects and accidents. It

should be read by anyone consulting

this memorandum for the first time;

Design considerations contains

information relevant to the specification

and installation of new washer-

disinfectors. It discusses the

requirements for each type of washer-

disinfector and outlines the

specifications to be included in any

contract. Practical considerations for the

installation of washer-disinfectors are

discussed including siting, heat

emission, ventilation, noise and

vibration, and mains services with an

emphasis on steam quality;

Validation and verification covers all

aspects of validation and periodic

testing of washer-disinfectors. It includes

detailed schedules and procedures for

tests and checks to be carried out for

commissioning and performance

qualification and for subsequent

periodic testing.

About this publication

Executive summary

HTM 2030 gives guidance on the choice, specification,purchase, installation, validation, periodic testing,operation and maintenance of washer-disinfectors (WDs)1in use in the National Health Service for processingmedical devices, laboratory ware and sanitary products.No guidance is given on WDs intended for use inprocessing textiles or for dishwashers in general cateringapplications.

This HTM is intended as a guide for technical personnelwith appropriate training and experience and also forusers responsible for the day to day running of WDs. Itwill also be of interest to architects, planners, estatesmanagers, supplies officers, and others in both the publicand private sectors.

Detailed information on the planning and design of asterile services department including the provision of WDsis given in Health Building Note 13 –‘Sterile servicesdepartment’ (Scottish Hospital Planning Note 13 applies tothe NHS in Scotland). Guidance for laboratory installationscan be found in Health Building Note 15–‘Accommodation for pathology services’ (ScottishHospital Planning Note 15 applies to the NHS in Scotland).

Although this edition of HTM 2030 reflects current WDtechnology it is recognised that considerable scope existsfor improvements in the operational and managementstandards used with WDs.

The term washer-disinfector is abbreviated to’WD’throughout this publication.

The current British Standards for WDs, although only inforce since 1993, are expected to be replaced byEuropean Union (EU) Standards within the next two tothree years. These Standards include consideration of therequirements arising as a result of EU Directives onmedical devices which affect WDs in two ways: firstly,some WDs will themselves be considered to be medicaldevices and therefore must meet the relevantrequirements of the Medical Devices Directive; andsecondly, the manufacturer of a medical device which isintended to be reprocessed is required to specify themethod to be used for reprocessing which will include anynecessary washing and disinfecting stage.

When practicable the information in this HTM has beenaligned with existing or anticipated Standards and adviceis offered when no standard has yet been formulated.

The WDs described in this HTM may not be suitable,without modification, for safely processing articlescontaminated with either Hazard Group 4 Pathogens orwith agents which are unusually resistant to disinfection.

1

Contents

About this publication

Executive summary

1.0 General page 51.1 Introduction1.4 Purpose of washer-disinfectors1.11 Legal framework for washer-disinfectors

1.11 Medicinal products1.15 Medical devices1.20 Published standards

1.24 Washer-disinfectors as medical devices1.27 Personnel1.44 Water supply1.45 Safety

2.0 Procurement of a washer-disinfector – anoverview page 11

2.1 Introduction2.2 Purchasing a washer-disinfector:2.3 What type of load is to be processed?2.4 What suitable washing-disinfection processes are

available?2.5 What models are available?2.6 Where will the washer-disinfector be sited?2.7 What services are available?2.8 Who will operate the equipment?2.9 What capacity is required?2.10 What ancillary equipment is required?2.12 What Standards or specifications are relevant?2.13 What sort of contract?2.14 Which manufacturer?2.15 What installation and commissioning

arrangements?2.16 What arrangements for service and repair?2.17 What are the likely running costs?

3.0 Choice of washer-disinfector page 143.1 Introduction3.2 Classification of washer-disinfectors by nature of

load to be processed3.4 Clinical washer-disinfectors

3.4 Human waste containers3.7 Surgical instruments and associated products3.11 Endoscopes3.15 Dishwashers

3.17 Laboratory washer-disinfectors3.17 Laboratory equipment3.18 Pharmaceutical equipment

3.20 Classification of washer-disinfectors byconfiguration/load handling type3.21 Cabinet (single chamber) machines (Type 1)

3.24 Continuous process machines (Type 2)3.28 Classification of washer-disinfectors by nature of

the process3.29 Cleaning3.35 Disinfection3.38 Drying

3.41 Liquid chemical sterilization3.45 When is a washer-disinfector required?3.48 Choice of washer-disinfector3.51 Cycle variables3.65 Sizes and numbers3.67 Assessment of workload and throughput

3.71 Aggregated workload and throughput capacity

3.72 Throughput capacity3.74 Throughput time

3.76 Sizing calculation3.76 Cycle time3.79 Machine capacity3.80 Aggregated workload for theatres3.83 Workload estimate3.84 Throughput estimate3.85 Number of machines required

3.86 Clinical washer-disinfectors for surgical instruments and associated products

3.89 Clinical washer-disinfectors for human-waste containers

3.93 Clinical washer-disinfectors for anaesthetic accessories

3.98 Clinical washer-disinfectors for endoscopes3.99 Rigid endoscopes3.103 Flexible endoscopes3.107 Clinical washer-disinfectors for use in

general practice3.110 Laboratory washer-disinfectors

4.0 Specification and contract page 304.1 Introduction4.2 Preparing a specification4.8 General design considerations

4.13 Safety features4.18 Over pressure protection4.19 Instrumentation4.29 Programmable electronic systems4.33 Steam supply4.34 Doors4.39 Materials of construction4.46 Integral air compressors4.49 Integral calorifiers and tanks4.52 Dosing systems4.58 Door controls

4.58 Control of manually operated doors

4.60 Control of doors of a double-ended WD

4.65 Internal doors and access ports4.66 Loading systems

‘ 4.79 Cleaning the washer-disinfector4.81 Invitation to tender4.86 Contract4.91 Delivery

5.0 Siting page 415.1 Introduction5.4 Operating department dirty utility room5.5 Endoscope cleaning room5.8 Sterile services department

5.8 Decontamination area

6.0 Engineering services page 436.1 Introduction6.5 Electrical services6.10 Steam

6.12 Steam for indirect heating6.22 Steam for direct heating6.27 Integral steam generators6.30 Condensate recovery

6.31 Compressed air6.32 Mains supply6.34 Local compressor6.37 Air quality

6.40 Drainage6.50 Hazardous effluents

6.54 Ventilation6.59 General room ventilation6.65 Machine ventilation

6.78 Chemical additives

7.0 Water supply page 537.6 Water hardness7.19 Ionic contaminants7.21 Microbial population7.23 Bacterial endotoxins7.25 Water treatment

7.26 Chemical purity7.27 Water softeners7.31 Integral water softener7.34 De-ionisers7.39 Reverse osmosis (RO)7.41 Distilled water7.44 Microbial purity7.51 Pipework7.53 Water supply bye-laws

8.0 Chemicals and additives (detergents, enzymic cleaners, rinse aids, lubricants anddisinfectants) page 60

8.1 Introduction8.3 Compatibility with the materials of

construction of the washer-disinfector8.5 Compatibility with the process8.6 Compatibility with the items to be processed8.8 Compatibility with the quantity of water8.10 Compatibility with other chemical additives8.12 Compatibility with subsequent

decontamination processes8.13 General8.16 Detergents8.21 Enzymic cleaners8.33 Cleaning additives for ultrasonic cleaners8.34 Rinse aids8.35 Lubricants8.37 Disinfectants and/or sterilants

8.37 Choice of disinfection method8.40 Criteria for selecting a chemical disinfectant8.50 Materials compatibility8.52 Safety of disinfectants

9.0 Washer-disinfectors for human-wastecontainers page 67

9.1 Introduction9.5 Choice9.7 Load handling equipment9.10 Standard specifications9.12 Additional specifications9.17 Operating cycle9.18 Disinfection requirements9.22 Drying stage9.24 Instrumentation/recorders10.0 Washer-disinfectors for surgical instruments and

associated equipment Page

10.1 Washer-disinfectors for surgical instrumentsand associated equipment page 70

10.1 Introduction10.4 Type 1 machines10.6 Type 2 machines

10.11 Standard specifications10.13 Additional specifications10.16 Load handling equipment10.20 Operating cycle10.21 Disinfection requirements10.22 Drying stage10.25 Instrumentation/recorders10.28 Test connections

11.0 Washer-disinfectors for anaesthetic accessories page 74

11.1 Introduction11.7 Load handling equipment11.11 Standard specifications11.13 Operating cycle

2

Contents

11.14 Disinfection requirements11.17 Drying stage11.21 Instrumentation/recorders

12.0 Washer-disinfectors for endoscopes page 7712.1 Introduction12.6 Standard specifications12.9 Additional specifications12.10 WDs with a chemical disinfection stage12.22 Load handling equipment12.25 Compatibility with items to be processed12.27 Disinfection requirements12.30 Rinse water: quality requirements12.35 Operating cycle requirements12.38 Drying stage12.40 Decontamination of the washer-disinfector12.47 Requirements for control of the disinfection stage12.48 Instrumentation/recorders12.51 Test connections

13.0 Laboratory washer-disinfectors page 8413.1 Introduction13.6 Load handling equipment13.7 Standard specifications13.9 Operating cycle13.10 Choice of detergent/cleaning agent13.12 Disinfection requirements13.13 Drying stage13.14 Instrumentation/recorders13.16 Test connections

14.0 Ultrasonic cleaners page 8714.1 Introduction14.7 Applications14.12 Standard specifications14.13 Additional specifications14.21 Wash cycle14.24 Type 1 ultrasonicators

14.24 Load handling equipment14.27 Type 2 (continuous process) ultrasonicators

14.30 Load handling equipment14.32 Instrumentation/recorders

Appendix I: Glossary of terms page 90

Appendix II: Abbreviations page 93

Appendix III: Useful addresses page 94

Appendix IV: Information to be supplied by themanufacturer page 95

References page 98

About NHS Estates page 105

3

Contents

5

Introduction

1.1 This volume of HTM 2030 covers the specification, purchase andinstallation of the various types of washer-disinfectors (WDs) used in hospitals,laboratories and other healthcare facilities.

1.2 Terminology used in washing and disinfection has long beeninconsistent and this has often led to ambiguities. This HTM introduces a setof terms which it is hoped will provide workers in this field with a standardvocabulary consistent with EU Standards which are to be introduced in thenear future. The glossary contains defined terms referred to in this volume ofHTM 2030.

1.3 Full references for all the documents referred to in this volume and forselected documents providing additional information of which the readershould be aware are listed at the end of this document.

Purpose of washer-disinfectors

1.4 WDs are used to decontaminate items intended for re-use. They maybe used in relation to both medical devices and medicinal products as well asother items. For example, they may be used for reprocessing, within theirintended use, medical devices, sanitary equipment, laboratory equipment,manufacturing equipment (for use in the manufacture of medicinal productsor medical devices) or cutlery and crockery.

1.5 The decontamination process is intended to:

• make the item safe for staff to handle;

• make the item safe for use on a patient (after any necessary additionalprocessing) – including when relevant ensuring freedom fromcontamination that could lead to an erroneous diagnosis.

1.6 WDs may also be used as part of the manufacturing process formedical devices, medicinal products, in vitro diagnostics or laboratory products– in processing “single-use” products or components such as bottles and vials.

1.7 When items being decontaminated by a WD are intended to be usedagain without further treatment (such as a terminal sterilization process)before being re-used the disinfection process in the WD must produce an itemwhich is microbiologically safe for its intended use.

1.8 When the items being decontaminated by a WD are intended to besubjected to further processing (such as a terminal sterilization process) beforebeing re-used the disinfection stage must produce an item which ismicrobiologically safe to be handled during preparation for subsequentprocessing.

1.9 The decontamination process involves two distinct stages: cleaning andmicrobial inactivation. The latter may be achieved by disinfection, sterilizationor both (disinfection followed by sterilization). WDs are used to

1.0 General

decontaminate items intended for re-use by subjecting the items to anautomated process of cleaning and disinfection.

Figure 1 Elements of the decontamination process

1.10 The efficacy of the cleaning stage of the process is of crucialimportance to the successful outcome of the disinfection stage. This isespecially relevant under the circumstances when a liquid chemical disinfectionor sterilization process has to be used.

Legal framework for washing and disinfection

Medicinal products

1.11 The manufacture and supply of medicinal products are controlled byextensive legislation based on EU Directives for medicinal products. These areenacted in the UK by the Medicines Act and a number of Regulations.

1.12 The requirements for the manufacture and supply of medicinalproducts are set out in the ‘Guide to good manufacturing practice formedicinal products’ (GGMP) published in Volume IV of ‘The rules governingmedicinal products in the European Community’.

1.13 The GGMP contains guidance on cleaning of components andmanufacturing equipment which have implications for the design, installationand operation of WDs. When a WD is to be installed for processing containers,components or manufacturing equipment for use with medicinal products theGGMP should be consulted at an early stage.

1.14 Guidance on the application of medicines legislation to particular casesis beyond the scope of this HTM and advice should be sought from theMedicines Control Agency (MCA) when necessary.

6

1.0 General

DECONTAMINATE

CLEAN

FLUSH +

+

WASH

Physical removalof gross soilingwith copiousqualities of water

Aqueous mediumtogether with:detergents;enzymic cleaners;ultrasonication;water jets etc asappropriate

DISINFECTAND OR

STERILIZE

Thermal or chemicaldisinfection, asappropriate to yield aproduct which iseither safe for re-use,or safe to handle forinspection, re-assembly, packingand sterilization priorto use

Medical devices

1.15 HTM 2030 ‘Operational management’ refers to the three EU Directiveson the manufacture and supply of medical devices and in vitro diagnostics.

1.16 Whether, and if so under what circumstances, the Medical DevicesDirective (93/42/EEC) applies to medical devices which are being reprocessedfor further use – either within a particular healthcare facility or externallyunder a service contract – is a complex issue beyond the scope of this HTM.Guidance is given in the MDA Directives Bulletin 18. If necessary furtheradvice should be sought from the Medical Devices Agency (MDA).

1.17 The essential requirements of the Medical Devices Directive are, interalia:

• that devices and manufacturing processes be designed to eliminate orreduce as far as possible the risk of infection to the patient, user andthird parties (annex I, paragraph 8.1);

• that devices must be designed, manufactured and packed in such away as to minimise the risk posed by contaminants and residues to thepersons involved in the transport, storage and use of the devices and tothe patients (annex I, paragraph 7.2).

1.18 There is no direct equivalent of the GGMP for medical devices. Thesame role is fulfilled by general quality system Standards (the BS EN ISO 9000series), supplemented by Standards tailoring the requirements specified in thegeneral standard for medical devices (BS EN 46001 and BS EN 46002) andStandards providing guidance on compliance with these Standards (EN 724and EN 50103).

1.19 These are mandated Standards and as such compliance with themaffords the presumption of compliance with the relevant essentialrequirements of the Directive.

Published Standards

1.20 British Standard 2745: 1993 specifies requirements for WDs formedical purposes. The standard is in three parts: Part 1 ‘Specification forgeneral requirements’; Part 2 ‘Specification for washer-disinfectors for human-waste containers’; and Part 3 ‘Specification for washer-disinfectors exceptthose used for processing human-waste containers and laundry’.

1.21 There are no EU Standards, as yet, for WDs. CEN Technical CommitteeTC 102 is developing a series of mandated Standards relevant to the MedicalDevices Directive for WDs. There are four parts with the working titles:‘General requirements’; ‘Washer-disinfectors for human-waste containers’;‘Washer-disinfectors for medical devices and surgical instruments’; and‘Washer-disinfectors for thermolabile medical devices (eg endoscopes)’. IECTechnical Committee TC 66 is developing Standards for ‘Safety requirementsfor washer-disinfectors’. When published, compliance with these Standardsmay be used to give a presumption of conformance to the relevantrequirements of the Medical Devices Directive.

1.22 This edition of HTM 2030 has been written while the new Standardsare in the course of development. The advice given here is designed to bebroadly consistent with the emerging Standards, but, HTM 2030 should notbe regarded as a substitute for the Standards themselves when ascertainingcompliance with EU Directives and the UK Regulations that implement them.

7

1.0 General

1.23 When a WD is purchased with the intention of processing both medicaldevices and components or equipment for use in the manufacture of medicinalproducts purchasers should ensure that the requirements for both types ofload are met.

Washer-disinfectors as medical devices

1.24 The Medical Devices Directive (93/42/EEC) Annex IX, ClassificationCriteria, Rule 15 classifies as medical devices “all devices intended specificallyto be used for disinfecting medical devices” and places them in Class IIa forconformity assessment purposes. It specifically excludes products that areintended to clean medical devices, other than contact lenses, by means ofphysical action.

1.25 WDs for cleaning and disinfecting medical devices are thus covered bythe medical devices legislation and those supplied on or after 14 June 1998will have to bear the CE marking in accordance with the provisions of theMedical Devices Directive.

This will apply to many of the WDs described in this HTM.

1.26 Detailed guidance on the application of medical devices legislation toparticular cases is beyond the scope of this HTM and advice should be soughtfrom the Medical Devices Agency.

Personnel

1.27 The following personnel are referred to in this volume of HTM 2030.Further information, including qualifications and areas of responsibility, can befound in HTM 2030 ‘Operational management’ and in Volume 1 of HTM 2010 ‘Sterilization’.

1.28 Management is defined as the owner, occupier, employer, generalmanager, chief executive or other person of similar authority who is ultimatelyaccountable for the operation of the premises. Depending on the nature of theorganisation, this role may be filled by the general manager, chief executive,laboratory director or other person of similar authority. In small autonomousunits the user may take on this function.

1.29 The User is defined as the person designated by management to beresponsible for the management of the WD.

1.30 In a hospital the user could be a sterile services manager, theatremanager, endoscopy clinic manager, ward manager or laboratory manager; inprimary care he/she could be a general practitioner, dentist or other healthprofessional. When a WD is used to process equipment or containers for use inthe preparation of medicinal products the user is normally the productionmanager in charge of the manufacturing process.

1.31 The Competent Person (Pressure Vessels) is defined as a personor organisation designated by management to exercise certain legalresponsibilities with regard to the written scheme of examination of anypressure vessel associated with a WD described in the ‘Pressure Systems andTransportable Gas Containers Regulations 1989’. The shorter term“competent person” is used in this HTM.

‘The Pressure Systems andTransportable Gas ContainersRegulations (Northern Ireland) 1991’apply in Northern Ireland.

8

1.0 General

1.32 The Authorised Person (Sterilizers) is defined as a person designated bymanagement to provide independent auditing and advice on sterilizers andsterilization and to review and witness validation (see HTM 2010 Volume 1 fora full definition of the responsibilities of the Authorised Person (Sterilizers)with respect to sterilizers and the qualifications and experience required).AP(S) are also able to provide independent auditing and advice onwashing/disinfection and WDs and to review and witness validation of theseprocesses and machines. The abbreviation AP(S) is used in this HTM.

At the discretion of management the function of the AP(S) may be carried outby an independent person, not registered as an AP(S), but who candemonstrate, to the satisfaction of management, previous training andexperience appropriate to carry out the designated tasks in respect of WDs.

1.33 The Test Person (Sterilizers) is defined as a person designated bymanagement to carry out validation and periodic testing of sterilizers (seeHTM 2010 Volume 1 for a full definition of the responsibilities of the TestPerson (Sterilizers) with respect to sterilizers and the qualifications andexperience required). Test Persons (Sterilizers) who have received appropriatetraining should be designated to carry out validation and periodic testing ofWDs. The abbreviation TP(S) is used in this HTM.

1.34 The Maintenance Person (Sterilizers) is defined as a persondesignated by management to carry out maintenance and periodic testing onsterilizers (see HTM 2010 Volume 1 for a full definition of the responsibilitiesof the Maintenance Person (Sterilizers) with respect to sterilizers and thequalifications and experience required). Maintenance Persons (Sterilizers) whohave received appropriate training should be designated to carry out periodictesting of WDs. The abbreviation MP(S) is used in this HTM.

1.35 The Microbiologist (Sterilizers) is defined as a person designated bymanagement to be responsible for advising the user on microbiologicalaspects of sterilizing non-medicinal products. They should also be defined asthe persons responsible for advising the user on the microbiological aspects ofhandling, washing and disinfecting used medical devices. The shorter term“microbiologist” is used in this HTM.

1.36 The Control of Infection Officer is defined as a person designated bymanagement to be responsible for advising the user on all infection controlaspects.

1.37 The Production Manager is defined as a person designated bymanagement to be responsible for the production of medicinal products ormedical devices.

1.38 The Quality Controller is defined as a person designated bymanagement to be responsible for quality control of medicinal productsand/or medical devices with the authority to establish, verify and implementall quality control and quality assurance procedures.

1.39 The Laboratory Safety Officer is defined as a person designated bymanagement to be responsible for all aspects of laboratory safety includingequipment, personnel and training relating to safety matters, and ensuringcompliance with safety legislation and guidelines.

A list of suitably qualifiedauthorised persons is maintainedby the Institute of HealthcareEngineering and EstatesManagement.

9

1.0 General

1.40 An Operator is defined as any person with the authority to operate aWD. Their duties may include the noting of WD instrument readings,replenishment of consumable items, such as detergent, and simplehousekeeping duties.

1.41 The Manufacturer is defined as the person or organisation responsiblefor the manufacture of a WD.

1.42 The Contractor is defined as a person or organisation designated bymanagement to be responsible for the supply and installation of the WD, andfor carrying out the installation checks and tests. The contractor is usually themanufacturer of the WD.

1.43 The Purchaser is defined as the person or organisation who orders theWD and is responsible for paying for it.

Water supply

1.44 All the organisations responsible for water supply have the statutorypower to make and enforce bye-laws to prevent waste, excessiveconsumption, misuse or contamination of the water supply. The ModelWater Bye-laws form the basis for such bye-laws. WDs must be designed,constructed, installed, operated and maintained in accordance with therequirements of the relevant bye-laws.

Safety

1.45 Extensive guidance on the safe operation of the various types of WD isgiven in HTM 2030 ‘Operational management’. Guidance on safe practices intesting WDs is given in HTM 2030 ‘Validation and verification’.

1.46 Many of the chemical additives used in WDs and their associatedancillary equipment, eg water treatment plant, are corrosive, toxic or otherwisehazardous and require special provision for their storage and use.

1.47 The ‘Control of Substance Hazardous to Health (COSHH) Regulations’place, upon management, an obligation to ensure that suitable measures arein place to protect their staff and others affected by the work activity. Thesemethods may include both safe systems of work and the provision of a specialventilation system.

1.48 Some of the substances which may be used in WDs, in particular thoseemploying chemical disinfection or sterilization, have Occupational exposurelimits (OEL) set out in Guidance Note EH 40 published annually by the Healthand Safety Executive. These limits are statutory maxima but should not beregarded as representing a safe working exposure. Employers have a legalobligation to ensure that exposure is reduced as far as reasonably practicable.

1.49 The WD, including any special ventilation equipment necessary for itssafe operation, will be subject to the COSHH Regulations. These Regulationsalso include control of biological agents. This is of particular relevance to theoperation of WDs which are commonly used to process items that may beheavily contaminated with pathogenic organisms.

Detailed guidance on ventilationsystems is provided in HTM 2025.

Detailed guidance on the WaterSupply Bye-laws is provided in a guidepublished by the Water ResearchCouncil.

10

1.0 General

11

Introduction

2.1 This chapter gives a short synopsis of the steps involved in purchasinga WD. More detailed information, including information relevant to specifictypes of WDs, is given in subsequent chapters.

Purchasing a washer-disinfector

2.2 The purchase of a WD can be broken down into a stepwise sequenceof decisions. These are summarised in the following paragraphs (see alsoTable 1).

What type of load is to be processed?

2.3 A knowledge of the load(s) which will be processed by the WD is anessential pre-requisite in making the correct decision about which WD topurchase; the difficulty in obtaining a clean product, the standard ofcleanliness and the disinfection required vary for different product types. Forexample, some products with intricate interstices or long narrow lumensrequire specific provision if they are to be cleaned satisfactorily.

Purchasers should be aware of the need to specify all the items requiringprocessing to allow the tenderer to offer the most appropriate machine andaccessories.

What suitable washing-disinfection processes are available?

2.4 In this HTM, WDs are classified by:

• the product range which they are intended to process;

• their configuration and load handling type;

• the nature of the cleaning and disinfection process.

Eight product-specific categories are recognised but, in many cases, WDs areavailable in which a single machine is designed to process two or more ofthese product categories. Guidance on the selection of a WD is given inChapter 3.

What models are available?

2.5 Once the type of WD which will be required has been agreed salesliterature and product data sheets should be sought from a number ofmanufacturers. The development of EU Standards on WDs should widen thechoice open to purchasers. Guidance on the information which should besought is given in Chapter 4.

2.0 Procurement of a washer-disinfector – an overview

12

Where will the washer-disinfector be sited?

2.6 The location available for the WD will have a significant influence onthe type of machine which can be used. Many of the larger continuous processmachines require considerable space. Guidance on siting is given in Chapter 5.

What services are available?

2.7 A WD will require one or more of the following services: electricity,water, steam, compressed air, drainage, ventilation and chemical additive(detergent, rinse aid etc) supply. The manufacturer’s product data sheets willshow which services are required for each model. Determine which of theseare available at the proposed site and the capacities of each service. It may benecessary to plan for a new service which would add significantly to the costof the installation. Further information about services is to be found in Chapter6. Water supply is crucial and is discussed in detail in Chapter 7.

Who will operate the equipment?

2.8 If the equipment is to be sited in a general area, eg a ward sluice room,intended for use by a wide range of ancillary and nursing staff the machineshould be simple to operate and as foolproof as possible.

Conversely, a machine which will be located in a centralised processing unitunder the care of specially trained staff – whose sole or principle activity will bethe operation of the WD – may be a more complex machine offering a numberof different operational cycles and loading systems to optimise the washingand disinfection of diverse products.

What capacity is required?

2.9 Establish the likely daily and weekly work load, and the peak hourlywork load, that the WD will have to process. Calculate the number of WDsrequired to process the workload. Throughput figures for differentmanufacturer’s machines and different models within any given range varyconsiderably. For continuous process machines a distinction must be madebetween the time required to process one load and the total number of loadswhich may be processed in a period of one hour. Further guidance is given inChapter 3.

What ancillary equipment is required ?

2.10 A WD may require ancillary equipment such as water softeners, de-ionisation or reverse osmosis (RO) water treatment plant, steam generators, aircompressors, extract ventilation (with or without condensers), bulk storage anddispensing facilities for process chemicals.

2.11 In addition some WDs will require load staging facilities, before andafter processing, purpose-built load carriers for different categories of productand means for returning load carriers from the unloading side of the WD backto the loading side.


13

What Standards or published specifications are relevant?

2.12 Most WDs for clinical applications (see Chapter 3) should have beenconstructed to British Standards. EU Standards, which will supersede theBritish Standards in due course, are in preparation as this HTM is beingprepared. In some cases, eg for endoscopes, there are no published British orEuropean Standards and additional specifications will be required. Advice onpreparing a detailed specification for the WD is given in Chapter 4.

What sort of contract?

2.13 Once the specification has been completed a contract should be drawnup for the supply and installation of the WD. Chapter 4 gives guidance onsuitable forms of contract.

Which manufacturer?

2.14 Two or more manufacturers should be invited to tender for the supplyof the WD. While no manufacturer should be excluded unnecessarily from thetendering process they should not be invited to tender unless there is arealistic prospect of their being awarded the contract. Guidance on tenderingis given in Chapter 4.

What installation and commissioning arrangements?

2.15 Chapter 4 contains advice on the documentation that themanufacturer should provide with the WD. After delivery and installation, theWD should be subjected to a formal documented programme of installation,commissioning checks and validation testing. This is discussed in detail in HTM 2030 ‘Validation and verification’.

What arrangements for service and repair?

2.16 It is common practice for the initial purchase contract to include allservice and repair costs for the first year after installation, ie during thewarranty period. A number of manufacturers also offer an “extendedwarranty” facility which, for an additional fee, provides an all-inclusive serviceand repair option.

What are the likely running costs?

2.17 Advice should be sought at the time of tender on the operational costsof the various machines which would be suitable. The operational costsshould include the anticipated requirements for services (water, electricity,steam etc), consumable items (detergents, rinse aids etc) and maintenance.This data should be used in the evaluation of the tender bids.


Introduction

3.1 This chapter contains information relevant to the choice of a new WD.It discusses the different types of WD and the way in which they are classifiedin this HTM. It summarises the loads for which each type is suitable and givesguidance on choosing the size and number of WDs required for a givenapplication.

Classification of washer-disinfectors by nature of load

to be processed

3.2 This HTM groups WDs into two broad categories according to theirintended use, ie the nature of the load which they are intended to process:

• clinical WDs are designed to process medical devices which may beintended for use without further processing or may be subjected to aterminal sterilization process before further use.

• laboratory WDs are designed to process equipment for use in themanufacture of medical devices and medicinal products, or to processlaboratory goods that are neither medical devices nor medicinal productsand are not intended for use in the clinical care of patients.

3.3 WDs can be further classified both by their configuration/load handlingsystem and by the nature of the operational process.

Clinical washer-disinfectors

Human-waste containers

3.4 These are intended for use in emptying, cleaning and disinfecting bedpans, urinals, suction bottles and similar containers, and for the rigid supportsused to hold disposable bedpans.

3.5 They may have a large volume or mass of material to be removed(faeces, urine, blood, serum, mucous) and many of these materials have a highbiomass of potentially infective organisms.

3.6 The processed product will usually be used without further treatment.

Surgical instruments and associated products

3.7 These are intended for processing a wide range of products used inclinical practice. WDs may be dedicated for use with one particular category ofproducts or may be intended for use with a range of products, often by theuse of dedicated load carriers for each product type.

14

3.0 Choice of washer-disinfector

Surgical instruments

3.8 This includes the whole range of surgical instruments but someparticular instruments, such as those with long narrow lumens or intricateinterstices, may require disassembly and/or specific adaptors if they are to becleaned effectively.

Anaesthetic accessories

3.9 This includes tubing, face masks and re-breathing bags for bothanaesthetic use and for respiratory therapy and diagnosis.

Bowls and utensils (hollowware)

3.10 This includes instrument trays and containers, receivers, gallipots,specula etc.

Endoscopes

3.11 Endoscopes may be considered in two categories based on the methodof construction of the endoscope. This will often determine which of theavailable washing-disinfection processes is suitable. However, in all cases,users should seek advice from the manufacturer of the endoscope on themost suitable method of decontamination.

3.12 Rigid endoscopes and their accessories may often be processedthrough conventional WDs used for surgical instruments – provided the WD isfitted with appropriate load carriers which direct water and wash solutionsthrough the lumen(s).

3.13 Flexible endoscopes are often unsuitable for processing through aconventional WD – parts of the endoscope may not withstand immersion andvalved channels may not be accessible unless the valve is open during thecleaning process. In addition, most flexible endoscopes will not withstand theelevated temperatures used during thermal disinfection and drying in aconventional WD.

3.14 Dedicated WDs are available which are intended specifically forprocessing endoscopes. These may incorporate a chemical disinfection orsterilization stage or may require that, after processing in the WD, theendoscope is terminally sterilized using a suitable low temperature sterilizationprocess.

Dishwashers

3.15 Dishwashers in general are not covered by this HTM. However there isan occasional need for the crockery and cutlery used by immunologicallycompromised patients to be disinfected to a higher standard than is found instandard commercial or domestic dishwashers. Consideration should be givento using a terminal steam sterilization process for items processed through astandard dishwasher or to specifying a dishwasher with a thermal disinfectionprocess as shown in Table 2.

3.16 In the latter case the WD should be fitted with a temperatureindicating instrument to show the temperature attained during thedisinfection stage.

15


16


Laboratory washer-disinfectors

Laboratory equipment

3.17 Laboratory washers are available to process a range of laboratory items.These items may include bottles and vials – either new or after previous use –intended for containing reagents, culture media, etc and other laboratoryequipment, predominantly glassware. Most do not include a disinfection stageexcept when the WD has been designed for a particular application, eg animalcage washing and disinfection.

Pharmaceutical equipment

3.18 Laboratory washers specifically intended for processing equipment andcontainers for use in the manufacture of pharmaceutical or in vitro diagnosticproducts may be configured for a single product or family of products, eg vials,or may be required to process a range of items.

3.19 The process specification may include high requirements for cleaningefficacy and levels of process residuals. This may incorporate a disinfectionstage for items to be used without further treatment in the preparation of anon-sterile product.

Classification of washer-disinfectors by

configuration/load handling type:

3.20 WDs can also be classified by the construction of the WD and themanner in which the load is processed through the machine.

Cabinet (single chamber) machines (Type 1)

Installed machines

3.21 Type 1 machines have a single chamber in which the full range ofprocess stages are carried out. Type 1 machines may have more than onechamber but the full range of process stages are carried out in each chamber.They are batch process machines in which all stages of the cycle are completedon one chamber load before another load can be processed in that chamber.

3.22 These may have either a single door through which both loading andunloading takes place or double doors with one door being used for loadingand the other for unloading.

“Table top” machines

3.23 These are a particular category of Type 1 machines which have only asingle door and are distinguished by their small size – having a chamberwhich will not accommodate two standard sterilization modules (SSMs) eachof 600mm x 300mm x 300mm dimensions – and by their limitedrequirements for connected services. These machines can be operated byconnecting to a single phase outlet (normally drawing 20 Amps or less at230 V), a potable water supply and discharging into a domestic drain orsink.

They may be intended to be floorstanding or may be placed on a worksurface to provide a convenientloading height.

Continuous process machines (Type 2)

Sequential chamber machines

3.24 These all have double doors, ie a loading door at one end of themachine and an unloading door at the other end of the machine, and alsohave doors or some other means of segregation between adjacent chambers.

3.25 Sequential chamber machines have two or more chambers throughwhich the load is moved in sequence. Each chamber is employed for one, ormore, different stages in the process. Two or more loads may be processedsimultaneously, with the loads at different stages in the cycle at any one time.Adjacent chambers are separated by an intervening door.

Conveyor machines

3.26 These may be equipped with double doors, air-flow baffles at eachend, or a door at one end and an air-flow baffle at the other.

3.27 Conveyor machines have a continuously, or intermittently, moving loadcarrier which progresses the load through a series of tanks, chambers or zones– in each of which one stage of the process takes place. Two or more loadsmay be processed simultaneously, with the loads at different stages in thecycle at any one time. The separation between adjacent stages may be spatialonly or there may be baffles (eg strip curtains) interposed.

Classification of washer-disinfectors by the nature of

the process

3.28 WDs can be further classified by the nature of the process employed ineach of the three principle processing stages: cleaning, disinfection anddrying. A limited range of WDs also provide a chemical sterilization facility.

Cleaning

Flushing machines

3.29 Cleaning is achieved by flushing with water; no detergents areemployed.

Washing machines

3.30 Water and detergents are used to clean the product. Detergents actboth as wetting agents – in which the reduction of surface tension allowscontact with all surfaces – and also as a solvent and/or dispersant of soil.Enzymatic detergent systems are intended to work by converting insoluble soilinto a water-soluble form.

3.31 The mass of water and the force with which the water comes intocontact with the surface to be cleaned plays a significant part in the soilremoval process.

17


Ultrasonic machines

3.32 Ultrasound energy is used to effect the mechanical removal of soil fromthe surface of the product.

Solvent cleaning machines

3.33 These machines use cleaning processes which employ specific solventsin which the particular soils to be removed are soluble. An example of this typeof process is the de-greasing systems which employ organic solvents to removemineral oils. These processes are not commonly used in reprocessinghealthcare products and are not covered by this HTM.

Disinfection

Thermal disinfection

3.35 In this process disinfection is achieved by the action of moist heatmaintained on the surface to be disinfected at a particular temperature for aparticular time (see Table 2) or some other time-temperature relationship ofdemonstrated equivalence.

Chemical disinfection

3.36 Disinfection is achieved by the action of a solution of a microbicidalchemical maintained on the surface to be disinfected at a particularconcentration for a particular time at, or above, a specified temperature.

3.37 The removal of the chemical disinfectant after the disinfection stage isof importance also and must be achieved without compromising the microbialquality of the product.

Drying

3.38 Drying may be an integral part of the cycle, usually by the circulation ofhot air over the product, or may be provided as a separate drying cabinet.Some products, eg corrugated anaesthetic tubing, require prolonged dryingtimes and a separate drying cabinet can improve the productivity of the WD.

3.39 Solvent drying systems have also been used but their relevance islimited to specific applications.

3.40 A dry product can also be obtained by the flash evaporation of residualmoisture from product items which are hot following a high temperaturethermal disinfection stage. This method is often employed in low costmachines, eg bed pan washers.

Liquid chemical sterilization

3.41 Sterilization by means of solutions of microbicidal chemicals is alsoemployed for a limited range of products which, although required to besterile for their intended use, cannot be sterilized through conventionalterminal sterilization processes (see HTM 2010 ‘Sterilization’).

18


3.42 Key factors in determining the efficacy of the process include:

• the concentration of the chemical sterilant;

• the temperature at which it is used;

• the contact time with the product;

• the absence of inhibitory materials, such as residual soiling.

3.43 The removal of the chemical sterilant after the sterilization stage is ofimportance and must be achieved without compromising the microbial qualityof the product. The control of the microbial quality of the rinse water is criticalin this respect.

3.44 The sterile product obtained from a liquid chemical sterilization processis not usually packaged for transport and may not have been dried. Underthese circumstances the product is only suitable for immediate use and themachine must be installed close to the point of use. Prolonged storage (eg formore than two or three hours) may permit contamination to occur followedby the growth of a large microbial population. The storage conditions are alsoimportant determinants of contamination.

When is a washer-disinfector required?

3.45 For many products used in healthcare practice there are two choicesavailable:

• products which are intended to be re-used after they have beendecontaminated and subjected to any necessary reprocessing (egterminal sterilization);

• single-use products – ie those which are intended to be discarded afteruse.

3.46 Products which are intended to be re-used may be decontaminated, inaccordance with the manufacturer’s instructions, by:

• manual cleaning followed by disinfection and/or sterilization;

• machine cleaning followed by disinfection and/or sterilization;

• automated machine decontamination incorporating cleaning and

• disinfection (or more rarely sterilization).

For further guidance, see Device Bulletin 9501 ‘The re-use of medical devicessupplied for single-use only’ published by the Medical Devices Agency.

3.47 When both re-usable and single-use devices are available a choice mayneed to be made based on several considerations including: clinicalacceptability; economics; local constraints – such as the storage space neededfor single-use items or engineering services (electricity, water, drainage)required for a WD processing re-usable devices.

The decontamination andsubsequent re-use of itemsintended for single-use requiresextensive technical investigation toestablish the compatibility of theprocess and that the performanceof the item has not been impaired.To undertake such studies isbeyond the competence andexpertise of hospital departmentsand routine laboratories and israrely justified on economic terms.There are also serious legalimplications for both managementand user.

The microbicidal chemicals usedfor disinfection and sterilizationare usually toxic and may also besensitisers in low concentrations.Many have defined exposure limits(see HSE guidance on occupationalexposure). Control ofenvironmental emissions andpersonnel exposure are importantconsiderations in the design andoperation of the processingequipment and in the siting ofsuch equipment. Specificventilation provision may berequired.

19


This situation is most relevant in the disposal of human excreta from bed-dependent patients and is discussed in more detail in Chapter 9.

Choice of washer-disinfector

3.48 The choice of WD will be governed by the nature of the loads requiredto be cleaned and disinfected. Detailed guidance on appropriate processes fordifferent load items can be found in a number of documents: ‘Sterilization,disinfection and cleaning of medical equipment: Part 1 Principles’ published bythe Medical Devices Agency; ‘Sterilization and disinfection of heat labileequipment’; ‘Bed pan washers’ published by the Central Sterilising Club; and inHTM 2030 ‘Operational management’.

3.49 Purchasers should be aware that items suitable for a particular type ofWD may still require different operating cycles, which need to be specifiedbefore purchase.

Guidance on the modification of operating cycles to suit different loads isgiven in HTM 2030 ‘Operational management’.

More information about the different types of WD is given in Chapters 10 to14.

Advice on individual cases should be sought, if necessary, from the AP(S)before any decision is made. When a chemical disinfection process is beingconsidered the microbiologist should also be consulted.

3.50 Once the type of WD has been decided, preliminary enquiries should bemade with a number of manufacturers to obtain specifications and price lists.Table 1 indicates some of the information that will be useful for planningpurposes and which should be obtained at this stage.

Cycle variables

3.51 For the purposes of this HTM the following definitions have beenadopted.

3.52 The Cycle Variables are the physical factors – such as time,temperature, water volume, flow rate, pressure, detergent concentration – thatinfluence the efficacy of the cleaning and disinfection processes.

3.53 Most operating cycles have a stage in which the load is exposed to thedisinfection conditions for a specified length of time. This period is known asthe Holding Time (see Table 2).

3.54 The Disinfection Conditions are the range of conditions that mayprevail throughout the chamber and load during the holding time.

3.55 The holding time may be preceded by a period in which the disinfectionconditions are present in the chamber but not yet present on all surfaces ofthe load which are to be disinfected. This period is the Equilibration Time.

20


Table 1 Information to be obtained before inviting tenders

Information required Objective

The Standards to which the To confirm that the WD WD is designed and meets recognised constructed and a statement specifications for design, of compliance construction, safety and

performance

Installation data including theoverall dimensions and themass of the WD (fully loaded,the number of supports,)floor loading at each

To enable the user to The clearance space required establish whether thefor installation access proposed location is suitable

for the WD and the extent of the The mass of the principal any site improvement work supportcomponents required (see Chapter 5)

Access space required for maintenance

Doors and necessary spacefor movement of the doors

The usable chamber space To enable the user toexpressed as volume, the determine the capacity of principal internal dimensions the WD for the loads whichand the number of standard it is intended to processload carriers or load itemswhich can be accommodated

Specifications for each of the To enable the user to engineering services required establish that the required by the WD quality and quantity of each

utility required is present orcan be provided, and to assess operational costs

The mean and peak sound power To enable the contractor tolevels generated by the WD confirm that the sound(see BS 2745: Part 1 ) power level after installation

will not exceed thatspecified for the location(see Chapter 5)

A description of the operating To enable the user to cycle including overall cycle determine the throughput oftime(s) for classes of goods the WD and hence calculateto be processed, length of the number of WDs requiredindividual stages: cleaning, for the anticipated workloaddisinfection, drying

The maximum temperature which To enable the user to may be attained during each stage, assess their compatibilitythe range within which cycle with the anticipated loadvariables can be adjusted,the nature and quality ofchemical additives required

21


}

3.56 Together the equilibration time and the holding time constitute thePlateau Period. The plateau period can always be determined from theindicated or recorded temperature in the chamber during each cycle. Theequilibration and holding times cannot be ascertained unless the temperaturein that part of the load which is slowest to reach the disinfection temperatureis also being recorded or measured.

3.57 For thermal (moist heat) disinfection the disinfection conditions arespecified by a Disinfection Temperature Band, defined by a minimumacceptable temperature, known as the Disinfection Temperature, and amaximum allowable temperature.

3.58 The higher the disinfection temperature the shorter the holding timewhich will be required to achieve the same level of disinfection.

3.59 For liquid chemical disinfection/sterilization processes the plateau periodis equivalent to the Disinfectant/Sterilant Exposure Time. The holding timecan only be determined by thermometry when the chemical agent is suppliedat an elevated temperature to a load which was not pre-heated to the requiredtemperature.

3.60 The disinfection temperature band may also be quoted for liquidchemical disinfection/sterilization processes but is not a complete specificationof the disinfection conditions since the efficacy of such processes depends alsoon the concentration of the chemical agent.

Table 2: Thermal disinfection temperature bands

65 10 7073 3 7880 1 8590 0.2 b 9593 c 10 98

Notes.a. The disinfection temperature is measured at the surface to be disinfected.b. The exposure time of 1 second (as specified in BS 2745 Part1) is too short for reliable measurementand a minimum time of 12 seconds (0.2 min) should be used.c. This time/temperature relationship is only used for items known to be contaminated with largeamounts of pathogenic organisms, for example in laboratories.

3.61 The dispensed volume of the chemical additives (eg detergents),including the accuracy and reproducibility of the dosing system(s), should bespecified.

3.62 For WDs employing jet washing systems, the pump pressure and waterflow are also critical variables.

3.63 For ultrasonic cleaners, the frequency, amplitude and power density(Watts/litre of usable chamber space) are critical variables.

3.64 In all cases, the duration of each process stage must be determinedwith sufficient accuracy to ensure that consecutive cycles have the sameefficacy.

Maximum allowabletemperature (ºC)

Minimum exposuretime (minutes)

Disinfection a

temperature (ºC)

22


23


Sizes and numbers

3.65 Precise information on the sizes and numbers of WDs required forparticular applications is difficult to give since there are considerable variationsin patterns of use. The number of WDs required will depend on the cycle timeand the loading capacity of the machine and in some circumstances on theflexibility of operation that may be required, eg whether items to beprocessed can wait until there is a full load for the WD or need to beprocessed immediately. Within the clinical applications for WDs, the size andnumber will also depend on the configuration and load handling type and theoperational type. Guidance on calculating the size and number of WDsrequired for a particular application is given below.

3.66 The methods which may be used to estimate the size and number ofWDs varies with the application for which the WD is to be purchased. A detailed description of two approaches is given for WDs intended to beused to process surgical instruments and associated products with briefcomplementary notes for WDs for other applications. The cycle times quotedby manufacturers of WDs will usually be based on the assumption that thewater supply is no less than the mid-point of the specified range for anacceptable supply. It should be noted that lower pressures may significantlyextend cycle times.

Assessment of workload and throughput

3.67 A combination of different types of WD and cleaning processes willoften be required to deal with the extensive range of instruments to beprocessed, eg in an SSD. This needs to be taken into account in calculatingthe capacity (size and number) of WDs required.

3.68 The provision of separate drying facilities for items which are difficultto dry (eg corrugated tubing for anaesthetic and respiratory use) candramatically increase throughput by reducing overall cycle times.

3.69 Bowls and receivers occupy a large volume but are relatively easy toclean. For a large SSD, consideration needs to be given to using a relativelysimple washer to process bowls and receivers rather than occupying space in amore sophisticated machine which is better utilised processing more complexinstruments.

3.70 Two distinct methods of assessment should be considered:

• aggregated workload and throughput capacity;

• throughput time.

Aggregated workload and throughput capacity

3.71 For items in sufficiently plentiful supply, minimising the turn-roundtime (the time between receipt of the used item and its having beenreprocessed and made available for further use) is not a priority. Anassessment based on the weekly workload generated by users is appropriate.

Throughput capacity

3.72 Throughput capacity is affected by a number of variables.

These include:

• The number of operational hours per week for the department in whichthe WD is located.

• The machine utilisation factor expressed as a percentage of the numberof operational hours. This will be influenced by several factors including:

a. delivery schedules from clinical areas;

b. staff availability for loading and unloading(meal and comfort breaks may total one hour/day);

c. start-up and shut-down time each day (approx. one hour/day);

d. planned and breakdown maintenance time(approx four hours/week);

e. routine, periodic and annual testing.

3.73 Precise estimations are difficult to make and may have limited valuedue to continually changing and developing clinical workloads. HBN 13recommends an assumed utilisation factor of 60% for most types of WDs andin practice this is reputed to be appropriate.

Throughput time

3.74 Throughput time may be the controlling factor:

• for items, usually sophisticated and expensive devices such asendoscopes, where the shortest practicable turn-round time may berequired in order to maintain an effective clinical service;

• for items where anything more than a short delay in initiating processingwould be unacceptable (eg human-waste containers).

3.75 Throughput time is affected by three key factors:

• cycle time;

• machine capacity;

• machine availability.

Sizing calculation

Cycle time

3.76 The processing time varies depending upon:

• the number and the duration of the flushing and washing stages;

• the disinfection time;

• the drying time.

With modern microprocessor-based control systems, several cycle options maybe programmed into the same machine.

The cycle time may be adverselyaffected by inadequate services suchas low water pressure and low watertemperature.

24


3.77 Some WDs now include a load identification system which reads alabel attached to a load carrier in order to identify the nature of the load. Themachine then automatically switches to the required process cycle.

3.78 The cycle time may be determined from the WD manufacturer’sspecification either for the particular item to be processed or for the “worstcase” load for which the cycle time will equal or exceed that required for theproducts to be processed.

Machine capacity

3.79 The machine capacity, specified by the manufacturer, will normally bestated in terms of the number of “baskets” or “trays” that can beaccommodated in one load.

The EU standard on sterilizers EN 285 has standardised 600mm x 300mm x300mm as a single sterilization module. Rigid re-usable containers for use insterilizers are also standardised to fit either singly, or in multiples, within themodular unit. Current proposals in the committee draft for the EU Standardson WDs have adopted this size as the basic module for WDs also. However,until these Standards are finalised it will be necessary to determine the size ofthe baskets referred to by the manufacturer.

Aggregated workload for theatres

3.80 An approximate assessment of the workload can be determined fromthe total actual, or the expected, case load on a weekly basis.

3.81 Each case may be assumed to require the use of at least two basketsin the WD load carrier; one for the instruments and one for the Edinburghtray, instrument orientation tray or re-usable container used to package theinstrument set. Large instrument sets will often require additional baskets – egfor orthopaedic, cardio-thoracic or large abdominal sets – and careful notesshould be made of which specialities may be served by the installation.

3.82 Dedicated load carriers or separate provision (eg ultrasonics) will berequired for particular items eg micro-surgical instruments, laparoscopes andtheir accessories.

Workload estimate

3.83 The workload should be estimated from historical records ofoperational activity or based on proposed work loads.

Theatre case load per week = CS1

Number of acute beds = CA

Average number of machine baskets:– per theatre case = BS

1

– per acute bed/week = BA2

Workload: WTOTAL (= number of baskets to beprocessed/week)

WTOTAL = (CS x BS) + (CA x BA)

1. It may be necessary to carry out this assessment on the sum of several subsets when there are anumber of operating theatres with diverse instrument demands per case.

2. This assessment should be based on the total number of acute beds, including maternity andgeriatric, but excluding mental health. If a factor of approximately 0.2 baskets per acute bed isassumed, this should be sufficient to allow for demands from other areas with lower volumerequirements such as A&E, community, etc.

25


Throughput estimate

3.84 The following data are required to estimate the throughput

Machine baskets per load BNMachine cycle time (in hrs) 1 CTNumber of operational cycles per week HMachine utilisation (%) 2 A

1. If a number of different operating cycles are to be run with widely differing cycle times, it may beadvisable to calculate the workload and throughput separately for each category ofinstruments/process cycle and sum the individual components. Alternatively, a weighted mean cycletime may be calculated from the proportion of each cycle that is expected to be required.

2. An assumption of 60% utilisation is appropriate in most cases (see also HBN 13).

Then the throughput TTOTAL =BN x H x A baskets per week

CT

Number of machines required

3.85 The number of machines required may be calculated as follows:

WTOTAL: Workload as machine baskets per weekTTOTAL: Throughput as machine baskets/week/machine

No. of machines required =[WTOTAL]

[TTOTAL]

Worked example

If WTOTAL = 1400 baskets/weekand TTOTAL = 1600 baskets/week/machinethen no. of machines required =

[1400][1600]

= [0.875]= 1.0

Clinical washer-disinfectors for surgical instruments

and associated products

3.86 WDs for this application present the greatest diversity of operational,configuration and load handling types. They range from small table-top modelssuitable for use in general practice to large, fully automated continuousprocess models capable of processing the full range of surgical instruments,utensils, containers and anaesthetic accessories with high throughput rates.

3.87 WDs for small units where a single, low volume WD is adequate areconsidered under WDs for use in general practice.

3.88 Most WDs for surgical instruments and associated products, other thanflexible endoscopes, are located in centralised units such as sterile servicedepartments (SSDs).

26


Clinical washer-disinfectors for human-waste

containers

3.89 These machines are equipped with load carriers built to acceptstandard numbers and/or patterns of specified containers including bedpans,urine bottles, suction bottles and bedpan carriers (for use with disposablebedpans), raised toilet seats, commode bowls, enema and emesis containers.

3.90 The workload will depend on the number of beds to be served, thebed-dependency of the patients in these beds and the nature of the medicalor surgical speciality – for example an orthopaedic ward may be expected tohave a high level of bed-dependency.

3.91 Human-waste containers need to be processed as soon as possibleafter use if they are not to become offensive or a potential infection hazard.The peak workload and the maximum throughput are factors that need to beconsidered. A high proportion of bed-dependent patients may be expected touse a bedpan in the hour following breakfast and the capacity of the WDshould be sufficient to process this within an hour.

3.92 Two capacities of WD are widely available: one that will process onebed pan or two urine bottles per cycle; and one that will process two bedpans or four urine bottles. The latter affords more flexibility at times of peakdemand.

Clinical washer-disinfectors for anaesthetic

accessories

3.93 Many WDs for surgical instruments and associated products can beadapted to process anaesthetic accessories, eg corrugated tubing, face masks,airways – usually by the provision of a dedicated, interchangeable load carrier.

There are also dedicated WDs intended solely, or principally, for processinganaesthetic accessories.

3.94 Current clinical practice makes frequent use of single-use items and/orprotects patient connected circuitry from contamination by the use of filters.These have dramatically reduced the throughput of such items. In many SSDsonly those items used in respiratory diagnosis, where filters cannot be used,are sent for reprocessing.

3.95 When the projected throughput is low the use of a WD for surgicalinstruments with a suitable load carrier is to be recommended. However, thedrying stage will necessarily be greatly extended beyond that required forsurgical instruments leading to a longer cycle time.

3.96 When a higher throughput is anticipated but where it is still noteconomical to provide a dedicated WD for anaesthetic accessories,consideration should be given to the provision of a separate drying cabinet.

3.97 Capacity should be assessed based on the number of items of eachtype that can be processed in a single load.

Simple deluge washers (normallyused for bowls and utensils) andultrasonic washers cannot usuallydeal with anaesthetic accessoriesor other tubing.

27


Clinical washer-disinfectors for endoscopes

3.98 Users are reminded that they should seek advice from the manufacturerof the endoscope as to the most suitable method of decontamination.

Rigid endoscopes

3.99 Many rigid endoscopes and most of the re-usable surgical accessoriesused for minimal access therapy (MAT) can withstand steam sterilization andmay be processed through WDs employing a thermal disinfection stage tomake them safe to handle during packing, etc.

3.100 It is essential that the WD is designed or adapted to ensure that duringthe flushing, cleaning and disinfecting stages water flows though the lumen(s)of the device.

3.101 Many cabinet WDs and continuous process WDs of the discretechamber type can be equipped with dedicated load carriers to process rigidendoscopes, gas cannulae, etc. There are also a number of dedicatedendoscope cleaners including ultrasonic cleaners.

3.102 The capacity of the WD should be assessed on the number of items ofeach type that can be processed in a single load.

Flexible endoscopes

3.103 Most fibre-optic endoscopes cannot be processed in conventionalWDs used for surgical instruments. Fibre-optic endoscopes are unable towithstand the high pressures generated during the cleaning process or thehigh temperatures attained during the disinfection process. Dedicatedendoscope WDs are available.

3.104 In general, the re-usable accessories, biopsy forceps, etc can beprocessed through a WD for surgical instruments.

3.105 For most fibre-optic endoscopes, the throughput time is the criticalfactor. Most endoscope WDs will only accept one endoscope per cycle. Thosewhich will take two endoscopes or more may be of little benefit in reducingthroughput time unless each endoscope is accommodated in a separatechamber and cycles can be run independently.

3.106 The disinfection stage of WDs for fibre-optic endoscopes is also criticalsince there are few suitable terminal sterilization processes with sufficientlyrapid cycle times.

Clinical washer-disinfectors for use in general practice

3.107 These are generally small machines, eg “table-top” cabinet washers,intended for use in dental, medical or veterinary general practice, clinics,mortuaries, etc where there is a low level demand for thorough cleaning anddisinfection of surgical instruments and utensils such as bowls and receivers.

3.108 The maximum anticipated demand and required turn-round time willusually be readily identified by the user for comparison with the loadingcapacity and cycle times specified for the WD.

Many fibre-optic endoscopes arestated by the manufacturer to beincompatible with ultrasonic cleaning.

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3.109 Purchasers should note the importance of the effect of low watersupply pressure and, where a hot water supply is required, the effect of lowfeed water temperature on process cycle times.

Laboratory washer-disinfectors

3.110 Laboratory WDs, whether intended for use in a clinical laboratory or inthe laboratory of a manufacturer of a medical device or medicinal product, areequipped with one or more load carriers specific to the nature of the items tobe processed.

3.111 The number of each type of item that can be accommodated and thelength of the operating cycle may then be used to estimate throughput bycomparison with anticipated workload. This can be used to calculate the sizeand number of machines required.

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Introduction

4.1 This chapter discusses general specifications for WDs and the steps tobe taken in inviting tenders and issuing a contract. The validation procedurewhich begins on installation of the WD is discussed in detail in HTM 2030‘Validation and verification’.

Preparing a specification

4.2 Purchasers are strongly recommended to seek assistance from the AP(S)when preparing a specification for a WD.

4.3 Standards and other specification documents are continually beingupdated and purchasers should ensure that they consult the latest editions ofsuch documents, including any amendments issued after publication, to keepabreast of changing requirements. Advice should be sought from the AP(S) onthis.

4.4 Most WDs are constructed to British Standards or the Standards ofanother European country, eg the German Standards Authority (DIN). TheseStandards will eventually be replaced by EU Standards which should then bespecified by the purchaser. The relevant Standards are discussed under theStandards specification heading for each chapter.

4.5 In some cases the Standards specification may not be adequate forWDs to be used in the public service. In these cases additional specificationsare listed below for general design considerations and, where appropriate,under an additional specification heading in each chapter.

4.6 Details of the proposed location of the WD should be stated clearly inthe specification sent to suppliers.

4.7 Except where the manufacturer is responsible for installation of themachine the type and standard of packing and delivery of the WD should bespecified. When site conditions are likely to be poor and damage could occur asubstantial dust proof transit case may be necessary.

General design considerations

4.8 The following design considerations are applicable to all or most typesof WD, but are not necessarily required by the current Standards. Whenapplicable they should be included in the specification for any WD to beoperated in the NHS.

4.9 All WDs and associated equipment are classed as “work equipment”and should comply with the ‘Provision and Use of Work EquipmentRegulations 1992’ (see HTM 2030 ‘Operational management’). Purchasers arereminded that under the Regulations it is the responsibility of the employer,not the

30

4.0 Specification and contract

manufacturer, to provide a WD that is “suitable for the purpose that it is usedor provided”.

4.10 All WDs made or sold in the UK from the 1 January 1996 shouldconfirm to the ‘Emission and Immunity Requirements of the ElectromagneticCompatibility Regulations 1992’. This may be achieved by compliance with EN 50081 (Emission) and EN 50082 (Immunity). The manufacturer should beinformed of any local sources of electrical magnetic disturbance which mayeffect the operation of the WD.

4.11 For maintenance purposes one or more panels of free standing WDsshould be easily removable and replaceable.

4.12 Special foundations are not normally required. The weight of the WD,which can be as much as 2500kg for a large continuous process WD whenfully loaded, should be borne by at least four pads each measuring at least150mm x 50mm. Floor mountings should be designed to minimise vibration.

Safety features

4.13 Safety features should be designed in accordance with the ‘Britishstandard code of practice for safety of machinery BS 5304’ and the Europeanstandard for the ‘Safety of electrical equipment EN 61010’.

4.14 The design of the control system should ensure that the door can notbe opened until the cycle is complete. When a fault is indicated the doorshould only be able to be opened by a key code, or tool, when the WD isreturned to a safe condition.

4.15 The manufacturer should provide a list of all safety devices togetherwith their settings and methods of adjustment.

4.16 All safety devices should be designed to fail in a manner which doesnot cause a safety hazard to personnel.

4.17 A safety hazard should not be caused by an error in the control orindication system.

Over pressure protection

4.18 Over pressure safety valves should be fitted to protect componentsthat may be damaged by inadvertent high pressures. This includes anypressure vessel, eg the steam generator or compressed air reservoir, usedwithin the machine. The discharge from safety valves should be terminated ina safe position.

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Instrumentation

4.19 The WD should be fitted with means to verify and/or record theattainment of the specified process conditions. The nature and extent ofmonitoring should be commensurate with the intended use of the load andthe risk arising from the inadvertent use of an improperly cleaned ordisinfected load. Particular requirements for different types of WD aredescribed in subsequent chapters.

A “cycle control” recorder may be of value in fault diagnosis but does notprovide verification of attainment of the specified operating conditions.

4.20 Within this HTM and its subsequent volumes three levels of processverification are identified:

• Verification by the operator of the attainment of disinfection conditions– the WD is equipped with a temperature indicator, independent fromthe controller, to allow the operator to verify attainment of theprogrammed disinfection temperature.

• This may be used when, because of the intended use of the load, therisk arising from use of the product after an unsatisfactory disinfectionprocess is low. This may include, for example, WDs for human-wastecontainers.

• Verification by process record, independent from the controller, of theattainment of disinfection conditions – the WD is equipped with atemperature recorder, with sensors and signal processing independentfrom the controller, to record the attainment of the programmeddisinfection conditions.

This may be used when, because of the intended use of the load, it isnecessary to provide confirmatory evidence that the disinfection process hastaken place within the limits established during validation.

Verification by process record, independent from the controller, of theattainment of process variables affecting both the cleaning and disinfectionprocesses – the WD is equipped with a multi-channel recorder, with sensorsand signal processing independent from the controller, to record the processvariables which were determined during validation studies to be critical to thesatisfactory outcome of the cleaning and disinfection processes.

This may be used when, because of the intended use of the load, it isnecessary to provide confirmatory evidence that both the cleaning anddisinfection processes have taken place within the limits established duringvalidation. This may include WDs for products which will be used withoutfurther processing and where the risks arising from an unsatisfactory cleaningand/or disinfection process are unacceptable.

4.21 A temperature indicator, independent of the controller, should be fittedto all WDs having a chemical disinfection stage to enable the user to verify theattainment of the specified disinfection temperature.

4.22 WDs used in SSDs and other similar production environments shouldbe fitted with recorders to record process temperatures and the values ofother key variables, eg volume of chemical additive admitted.

The use of recording devices may berequired for compliance with thevarious quality systems under whichthe WD may be operated but inaddition may be cost effective inproducing the information to optimisethe decontamination process

WDs may be fitted with either, orboth, of two separate recordingsystems. A “cycle control” recorderwhich records the values of controlvariables as seen by the controller; ora “process verification” recorderwhich, independently of the controllerand its sensors, records the valuesattained for some or all of the criticalvariables which determine theadequacy of the process.

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4.23 When an instrument has a facility to allow it to be adjusted theadjustment should require the use of a key code, or tool, which is notavailable to the operator.

4.24 When a fault is indicated in the form of an error message shown on avisual display unit, it should be clearly distinguishable from the normalmessages – for example, by use of a different colour or larger size of text. Theindicator should remain displayed until cancelled by the operator.

4.25 The contractor should be required to carry out adjustments to theinstruments on site so that the accuracy specified at the disinfectiontemperature can be met with the plant running and under the conditionsnormally prevailing on site.

4.26 An indicator should show which stage of the operating cycle is inprogress and indicate “cycle complete” at the end of the cycle. Forcontinuous process machines, separate indication of the operational statusshould be provided for each chamber or section.

4.27 A five digit counter should be provided to indicate the cumulativenumber of cycles started. The counter should be non re-settable, tamperevident or sealed. For continuous process machines the counter shouldindicate the number of loads which have entered the WD.

4.28 Provision should be made for the attachment of the test instrumentsrequired for the tests specified in HTM 2030 ‘Validation and verification’.

For temperature testing – a connection should be provided to permit the entryof sensors into the chamber, as described in BS 2745 Part 1. A suitable formof temperature connection is described in EN 285, while a suitable gland forattachment to the connection is illustrated in Figure 3 of the ‘Validation andverification’ volume of this HTM.

For pressure or flow testing – test tees and valve cocks with sealing plugsshould be fitted to permit connection of test instruments for the verificationand calibration of all pressure and flow instruments permanently fitted to theWD.

When the WD is provided with instruments to monitor other variables – suchas electrical conductivity of water supply or ion selective electrodes (ISE) forthe determination of detergent concentration – means should be provided toenable test instruments to be connected to verify the readings obtained fromthe installed sensors.

Programmable electronic systems

4.29 Modern WDs frequently use programmable electronic systems (PES) forcontrol and data recording. Such systems should be designed in accordancewith the principles set out in the two parts of the HSE document‘Programmable electronic systems in safety related applications’.

4.30 When a PES is used to control or monitor the process, the values ofcycle variables critical to process performance and determined duringvalidation should be documented in the validation report regardless ofwhether or not they are held in the PES memory.

4.31 The version number of the software used in the PES should beavailable for display when required.

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4.32 Combined control and instrumentation systems that are whollyoperated by means of a PES should incorporate at least two timing systemsindependent of each other. When one timing system is used to control theholding time during the disinfection stage it is verified by the other timer.

Steam supply

4.33 When the WD is fitted with a steam supply, the steam pipework shouldinclude a pressure reducing system with a separator on the high pressure side.The system should be fitted with a strainer and trap to prevent condensateaccumulating in the system.

Doors

4.34 WDs may have a single door or a door at each end (double door orpass through machines). Double door machines are preferred since theyallow full physical segregation of clean disinfected items from dirtycontaminated items. However, the increased complexity of a two doorsystem may present additional maintenance requirements. Without specialprovision these may be inadequate for effective use of the WD as a “pass-through” machine from a “dirty” to a “clean” area since they allow acontinuous, large, loss of air from the clean area.

4.35 Other continuous process machines may be in the form of a series oftanks into which the load is moved by an overhead conveyor. Each tank isprotected by horizontally hinged spring loaded flaps which are pushed open bythe load as it is lowered into, or raised from, the tank.

4.36 Discrete chamber or cabinet type machines (Type 1) may be fitted withmanual or power operated doors whereas continuous process machines (Type2) are normally fitted with power operated doors. Power operated doors willusually be vertical sliding doors. When manually operated doors are used theymay be either vertically hinged or horizontally hinged. Horizontally hingeddoors which fold down may offer the additional benefit of providing a loadingand/or unloading platform.

4.37 The choice of design for any particular installation will depend on theworkload, space restriction, price and ease of maintenance. If hinged doors arespecified it should be clearly stated whether they are to be hinged on the lefthand side, the right hand side or horizontally hinged.

4.38 It should be possible to clean the contact surfaces of the door sealwithout removing parts of the WD.

Materials of construction

4.39 Those parts of the WD which come into contact with the load shouldbe manufactured from materials which have corrosion and abrasion resistantproperties equal to or better than stainless steel (304 series to BS 1449: Part 2:1983).

4.40 The wet and chemically aggressive environment within the WD willcause corrosion and galvanic attack when dissimilar metals come into contact –a fact which should be taken into account when choosing the materials ofconstruction.

Some continuous process machinesare fitted only with baffle stops ateach end of the machine, and insome cases between sections of themachine.

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4.41 The chamber should be designed to withstand 25,000/T operatingcycles where T is the minimum operating cycle time in hours, specified by themanufacturer.

4.42 The method of construction of the chamber should ensure that it isself draining and free from sharp internal corners which cannot be cleanedduring the normal cleaning cycle.

4.43 Floor mounted WDs shall be fitted with adjustable feet to compensatefor irregular surfaces.

Integral steam generators designed to operate at pressures exceeding200 mbar gauge

4.44 Steam generators fitted to WDs should be designed and manufacturedto conform to BS 5500: 1991.

4.45 The integral steam generator should be equipped with blow downfacilities to enable sludge to be expelled.

Integral air compressors

4.46 WDs may require a supply of compressed air for either the operationof valves and powered door systems and/or during the drying stage of thecycle.

4.47 When compressed air is intended to come into contact with thewashed and disinfected product the compressed air supplied should be“medical grade” ie it should be oil and particulate free (see HTM 2022).

4.48 Built-in air compressors should be suitable for the duty imposed uponthem. Current experience suggests that certain small compressors of the typefitted to domestic refrigerators are not suitable for use in WDs. Withoutmeticulous maintenance a small air leak can cause them to run continuouslythus causing carbonisation of the oil and a consequent failure of the WDpneumatic system.

Integral calorifiers and tanks

4.49 All integral calorifiers should conform to BS 853: 1990 and should bedesigned and constructed to allow thermal disinfection to be achievedthroughout the calorifier and associated pipework before water and/or steamcan be supplied to the WD during the thermal disinfection and subsequentstages.

4.50 Water tanks within the WD should be self draining and located so thatthey are cleanable by the operator and fitted with a drain down system whicheither works automatically when the machine is switched off or which isaccessible to the user.

4.51 All tanks should be fitted with an overflow (see Water UndertakersBye-laws 1989).

When water is to be heated the heat source should be controlled by athermostat and it should employ a heating medium as specified by thepurchaser. The heat sources should be removable for replacement ormaintenance purposes.

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Dosing systems

4.52 The WD should be fitted with not less than two systems forcontrolling the admission of chemicals (detergents, disinfectants, rinse aids,lubricants etc.) and should be provided with the facility for at least oneadditional dosing system to be fitted.

4.53 Each dosing system should be provided with means to adjust thevolume admitted. Access to the means of adjustment should require the useof a key, code or tool.

4.54 The stage(s) in the process cycle at which each dosing system admitschemical to the WD should be under the control of the automatic controller.

4.55 Each dosing system should be provided with means to determine thevolume admitted and the time within the operational cycle when theadmission occurred. This data should be available to the operator.

Failure to admit the specified minimum volume should cause a fault to beindicated.

4.56 The manufacturer should specify the accuracy and reproducibility of thecontrol of volume admitted for each of the dosing systems used (detergents,disinfectants, rinse aids, lubricants) per cycle.

4.57 The WD should be fitted with a system that will indicate when there isinsufficient chemical(s) available for the next cycle.

Door controls

Control of manually operated doors

4.58 An explanation of the manual action required to lock the door shouldbe provided for the operator. In addition, if the unlocking procedure is not thereverse of the locking procedure, there should be an indication to the operatorof the manual action required to unlock the door.

The indication should be clearly displayed either on the door or on its handleor handwheel. Explicit instructions should be displayed on the facing paneladjacent to the door or on the operator’s control panel.

4.59 The door mechanism should be such that the force to be applied by anoperator in order to either lock or unlock the door does not exceed 250N atthe intended point of grip.

Control of doors of a double-ended WD

4.60 In double-ended WDs the control initiating the automatic cycle shouldbe at one end only. When the loading door is closed and locked, it should notbe possible to open the unloading door until the WD has completed asuccessful operating cycle – ie without showing a fault.

4.61 If a fault develops, it should only be possible to open the loading door.

4.62 It should not be possible for an operator to open or close a door at theopposite end of the WD or for more than one door to be open at one time.

The means of adjustment can bemanual or automatic.

This requirement does not apply toWDs for human-waste containers.

36


4.63 A visual display should be provided at both ends of the WD to indicatewhen the cycle is in progress.

4.64 The indication “cycle complete”, or an equivalent indication, should becancelled when the unloading door is unlocked, and the loading door shouldremain locked until the unloading door has been locked again.

Internal doors and access ports

4.65 Doors between consecutive sections of a multi-section machine andaccess ports fitted to the outside of the machine for maintenance purposesshall comply with the requirements of IEC 1403.

Loading systems

4.66 The WD should be provided with carriers to locate the load during thewashing and disinfection process. When interchangeable load carriers andbaskets are provided each load carrier should be capable of being fitted andremoved without the use of tools.

WD loading systems should be designed with regard to the Manual HandlingOperations Regulations 1992.

4.67 When the WD is supplied with a system for supporting the load –and/or a system for transferring the load into and/or out of the chamber – thefollowing should apply:

• the load should be wholly supported and retained within the usablechamber space for the duration of the operating cycle;

• the force required by the operator, either directly or by the applicationof a mechanical device supplied with the equipment, to remove thewhole, or part, of the load from the chamber should not exceed 250Nwhen loaded and operated in accordance with the manufacturer’sinstructions;

• the load carrier should either be retained in the chamber by amechanism which is only released when the transfer system is in place,or remain stable when withdrawn for a distance equal to two-thirds ofthe chamber length, and be fitted with a retaining device, which has tobe released if the load is to be withdrawn further.

4.68 Means should be provided such that the transfer of the load into andout of the chamber does not cause damage and wear to the chamber.

4.69 The system used to support the load should be constructed fromdurable, corrosion-resistant materials and should withstand, without damage,the environment within the chamber.

4.70 The system used should neither prevent the attainment of the pre-setcycle variables nor the free drainage of water from the load and thepenetration of water and/or steam into the load.

The load carrier(s) should be designed so that they cannot be mis-positionedin a manner which will prevent such attainment.

Systems which cause high levels oflocal stress, eg point loadings, mayalso initiate corrosion in stainlesssteel materials.

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4.71 Any accessory used for handling the load which can be used outsidethe WD (eg a trolley) should remain stable when it is supporting its maximumdesign load and a force of 250N is applied horizontally in any direction to thehighest point of the load or accessory.

4.72 The trolley should be designed to allow the operator to align the trolleywith the WD for ease of loading and unloading.

4.73 The trolley should be provided with means to collect liquid residuesfrom the load to prevent these from dripping onto the floor. The meansprovided should be detachable for cleaning and for sterilization at 134–137°Cin a porous load sterilizer.

4.74 The trolley should be provided with swivel wheels to facilitatemanoeuvring.

4.75 The trolley should be provided with a parking brake.

4.76 The trolley should be designed to secure the load carriers on the trolleyduring loading and unloading, and while traversing a gradient at a slope of upto one in 20.

4.77 Trolleys intended for use with single door machines should be designedand constructed to facilitate cleaning and disinfection of the trolley betweenuse for dirty and clean loads.

4.78 Load conveyors outside the WD which are intended to, or mayreasonably be expected to come into contact with, soiled/contaminated goodsshould be designed and constructed to be easy to clean and disinfect. Whenpracticable the load conveyors should be demountable and be able to besterilized at 134–137°C in a porous load sterilizer.

Cleaning the washer-disinfector

4.79 The design, construction and operation of the WD should ensure thatduring the process the surfaces of the chamber and the load carrier presentedto the operator are cleaned and disinfected.

4.80 For manually filled and emptied cleaning machines with no disinfectioncycle, eg stand alone ultrasonic cleaners, the manufacturer should advise onthe cleaning/disinfection method.

Invitation to tender

4.81 Once detailed specifications have been drawn up, manufacturers shouldbe invited to tender for the supply and, if required, installation of the WD.

4.82 When inviting tenders purchasers should follow the principles describedin Chapter 2 of ‘Contracts and commissions for the NHS Estate’, published byNHS Estates.

4.83 The purchasers should specify that the WD manufacturer operates aquality system in accordance with the principles described in the EN 29000series and, when applicable, the EN 46000 series.

38


If the manufacturer has both designed and manufactured the WD the qualitysystem should conform with EN 29001/EN 46001.

If the WD has been manufactured to a design supplied by a third party themanufacturer’s quality system should conform to EN 29002/EN 46002.

In either case the manufacturer should ensure that each supplier ofaccessories, fittings and other materials also operates an appropriate qualitysystem.

4.84 Prospective contractors should be given the following information:

• that each WD will be subject to a validation process as described inHTM 2030 ‘Validation and verification’;

• unless otherwise specified, that the installation checks and testspecified in the validation process must be satisfactorily completedbefore the WD can be accepted;

• whether the installation checks and tests are to be witnessed by thepurchasers representative (normally the TP(S));

• the date by which all services will be available;

• the date by which the validation process is expected to be completed.

4.85 Under the Public Supply Contract Regulations an exceptionally lowoffer may only be rejected after the contracting authority has requested andtaken into account any explanation given by the supplier in writing (StatutoryInstrument 1995 No 201 Part V 21/71).

Contract

4.86 For procurement of WDs the following conditions of contract may beused:

• National Health Service – Conditions of Contract for the Purchase ofGoods (or Scottish equivalent);

• National Health Service – Conditions of Contract for the Supply andInstallation of Equipment;

• National Health Service – Conditions of Contract for the Maintenanceof Equipment.

Modifications to suit local purchasing policy may be required.

These documents are available from the NHS Supplies Authority, or fromScottish Healthcare Supplies for the Scottish equivalent (see Appendix III).

4.87 Consideration may also be given to the use of alternative forms ofcontract, for example MF/1 (available from the Institution of ElectricalEngineers, the Institution of Mechanical Engineers or the Association ofConsulting Engineers) or the Joint Contracts Tribunal (JCTT) suite ofdocuments (available from RIBA publications) or the New EngineeringContract issued by the Institution of Civil Engineers. Addresses are given inAppendix III.

4.88 Purchasers using other forms of contract are strongly advised to seeklegal advice especially where a contract proposed by the prospectivecontractor is being considered.

39


4.89 Other contracts – notably for the authorised person, test person,maintenance person, competent person, and microbiologist – may need to beconsidered at this time (see HTM 2030 ‘Operational management’ and Volume1 of HTM 2010).

4.90 In awarding these contracts purchasers should ensure that there is noconflict of interest that would compromise the validation process as set out inHTM 2030 ‘Validation and verification’.

Delivery

4.91 On or before delivery of the WD the manufacturer should provide thepurchaser with the information specified in Appendix IV.

WDs for a particular scheme should not be ordered and stored on site for longperiods prior to installation and validation. Disregard of this recommendationmay invalidate the manufacturer’s warranty and cause deterioration of the WDprior to installation.

40


Introduction

5.1 This chapter sets out some of the considerations to be taken intoaccount when siting a WD. WDs are commonly installed in sterile servicedepartments (SSDs), operating departments, wards and laboratories. Acomprehensive review of the requirements for SSDs is given in HBN 13 andfor operating departments in HBN 26.

5.2 The room in which a WD is installed and operated should meet therequirements of the Workplace (Health, Safety and Welfare) Regulations1992. These Regulations have considerable implications for the design ofaccommodation for WDs.

5.3 Fire safety precautions should comply with ‘Fire Safety: approvedDocument B’ of the Building Regulations 1991 and HTM 83 Fire Code. [Seealso Fire Safety, Policy and Principles for Health Buildings in Scotland, SHHD1988 P: SHHD/DGM (1988-61)].

Operating department dirty utility room

5.4 This area should be equipped for the storage, preparation for use, anddisposal of contents after use, of human-waste containers including vomitbowls, bedpans and urine bottles. Specific guidance is given in HBN 26.

Endoscope cleaning room

5.5 Provision may be made within the operating department for anendoscope cleaning room to provide facilities for cleaning and disinfection orsterilization of those endoscopes which cannot be returned to the central SSDor TSSU for reprocessing. When practicable this is best provided by means ofan automated endoscope WD. Manual cleaning facilities will also be required.

5.6 A toxic vapour extract system at bench level to exclude all possibility ofinhalation should be installed whenever a liquid chemical microbicide is to beused other than in an enclosed ventilated automatic WD.

5.7 The same area may also be used to accommodate an automated WDfor emptying, cleaning and disinfecting suction bottles.

Specific guidance is given in HBN 26.

Sterile services department

Decontamination area

5.8 A soiled returns hold area, where collection trolleys containing soiledreturns can be marshalled, is normally located adjacent to or within the

41

5.0 Siting

washing area and adjacent, or with easy access to, the hospital corridor orloading bay.

5.9 The washing area provides space to:

• off-load soiled returns from trolleys;

• sort items for disposal or appropriate cleaning and disinfection;

• clean and disinfect reprocessable items;

• transfer cleaned and disinfected items to the packing room.

When the transfer is automatic (ie from an automatic WD) means should beprovided to allow for the return of items which, when inspected in the packingroom, are found not to have been properly cleaned.

5.10 The necessary cleaning and disinfection processes for the routine rangeof items to be processed may require several different types of WD. These mayinclude, for example:

• Single door cabinet WDs which may be used with a pass through hatchto the packing room.

When a hot air drying cabinet is used this should be of the pass through typewith interlocking doors for transferring items from the washing area to thepacking area.

• Continuous process “pass through” WDs which will usually be equippedwith a conveyor system to return the load carriers from the packingroom to the decontamination room.

The conveyors should be designed and constructed to be easy to clean anddisinfect (see also paragraph 4.78).

The decontamination room should provide a facility for cleaning trolleys usedto transport returned items for decontamination and a suitable holding spacefor the number of trolleys which will be in use.

The room should also provide sorting benches with sufficient space forunloading trays from the trolleys and transferring items to WD baskets/loadcarriers.

Proper insulation of WD and exposed pipework from services is essential,together with appropriate ventilation, in order to maintain a comfortableworking environment.

5.11 Manual cleaning facilities may also be required. A stainless steel doublesink, double drainer and water gun unit (hot and cold water) should beprovided. The manual cleaning area should be provided with a hood andextract ventilation (to microbiological safety cabinet Class 1 – 0.7m/sec facevelocity) to protect the operator from aerosols created during the cleaningprocess.

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5.0 Siting

6.0 Engineering services

Introduction

6.1 A WD installation will require external service connections. These mayinclude water (of various qualities), electricity, steam, compressed air,drainage, ventilation and supplies of process chemicals.

6.2 The manufacturer should make clear at an early stage which serviceswill be needed and give detailed requirements for each service (see Table 3).

6.3 For most WDs the water and drainage services are the most criticalalthough for user comfort, especially in the case of WDs using chemicaldisinfectant/sterilant, the ventilation and extraction system are also ofimportance.

6.4 If the services are to be installed by a contractor, other than thecontractor installing the WD, care must be taken to ensure that the size andlocation of terminations are agreed before the contracts are placed.

Table 3 Information on services to be obtained from the washer-disinfectormanufacturer

Steam a) acceptable range of supply pressures;b) maximum flow and usage rates;c) usage per operating cycle;d) when steam is generated within the WD, the

acceptable limits for hardness, pH and conductivity of feed water.

Electricity a) type of supply eg AC or DC;b) number of phases (normally one or three) and

whether neutral is required for a three-phase supply;c) supply voltage and frequency including nominal and

acceptable minimum and maximum values;d) maximum continuous power demand in kW or kVA.

Compressed air a) acceptable range of supply pressures;b) the flow required at minimum pressure;c) the volume of air used for each cycle;d) the quality or quantity of air required including dew

point, maximum size and concentration of particulate material, oil content and microbial contaminationlevel as relevant.

Water For each grade of water required,a) the acceptable range of supply pressures;b) the flow at minimum pressure;c) the volume used per cycle;d) the acceptable temperature range for incoming water;e) the quality of water required when relevant:

– the maximum permissible hardness expressed as mg/l CaCO3;

– the acceptable range of pH;– the maximum permissible conductivity;

43

– the limiting concentration of heavy metals, halides, phosphates and nitrates;

– the maximum acceptable microbial population.

Drainage a) the maximum flow of effluent to the drain;b) the maximum temperature of the effluent on leaving

the WD;c) the maximum effective diameter of the discharge

orifice from the WD chamberd) requirement for sealed drainage system if hazardous

fumes or gases are produced from chemicals used in the process.

Ventilation a) the peak value during a cycle and the average value throughout a cycle of the heat in watts transmitted to the environment when the WD is operated in still air at an ambient temperature of 23 ± 2°C;

b) the heat in watts transmitted by a full load being unloaded from the WD into still air at an ambient temperature of 23 ± 2°C;

c) the maximum flow of air extracted from the environment of the WD as exhaust ventilation;

d) ventilation requirements for removal of fumes or gases from hazardous chemicals used in the process.

Process chemicals details of all process chemicals required (eg detergents,rinse aids, sequestering agents, descalers, microbicides)for the operation of the WD, including any requirementfor regeneration of integral water treatment system), thequantity required per cycle, the nature and size ofcontainers in which they are supplied, the necessarystorage conditions and instructions for safe handling.

Electrical services

6.5 The electrical power requirements will depend on a number of factors,such as the type of WD and the method used to heat water, hot air dryers etc.Some WDs will need a three phase supply. The manufacturer should providedetails of the type of supply (AC or DC), number of phases, frequency andvoltage, with tolerances and loading.

6.6 Each WD should be connected via an isolator. The type of isolator willdepend on the nature of the supply:

• for small WDs and table top WDs with a maximum current demand notexceeding 13A on a single phase supply, isolation may be provided by asimple plug and socket connection using a correctly fused plug and aswitched socket-outlet;

• when a three phase and neutral supply is required or when themaximum demand from a single phase supply is more than 13A, theWD should be wired directly to the isolator. The switch should isolate allpoles simultaneously and each pole should be fused separately. Thecable from isolator to WD should be fixed and protected from theeffects of heat and water.

6.7 Within the loading area an additional switch should be provided so thatthe operator can electrically isolate the WD or group of WDs in the event

44


of an emergency. The switch should be placed between the normal operatingposition and the exit door.

6.8 It is not normally necessary for WDs to be connected to the essentialsupplies circuit, when this is available. Exceptions might include the decisionto ensure that one WD within the SSD remains on the essential suppliescircuit. Guidance on the supply of electricity in the event of failure of thenormal supply is given in HTM 2011 ‘Emergency electrical services’.

6.9 All electrical installations should conform to IEE Regulations containedin BS 7671. Further guidance is given in HTM 2007 ‘Electrical services: supplyand distribution’ and HTM 2020 ‘Electrical safety code for low voltagesystems’ (Escode–LV).

Steam

6.10 Steam may be used to supply a heat exchanger as a source of indirectheating for water or air to be used in the cleaning, disinfection or dryingstages of a WD operating cycle.

6.11 Steam may also be used to heat process water directly, or to heat theload directly during the thermal disinfection stage, and for this purpose maybe supplied either with an integral steam generator or from an external(“mains”) supply.

Steam for indirect heating

6.12 Steam heat exchangers used for heating water or air may be of theshell, tube or plate design. In all cases, the steam supplied should besubstantially free from non-condensible gases and free from oil since thesecontaminants will seriously impair the efficiency of the heating process. Theeffect of thin films of air on the surface of the heat exchanger may increaseheating costs by 25% or more.

6.13 Suitable steam may be available from the high-pressure hot watersystems used in some hospitals.

6.14 The steam service should be designed to meet the maximum demandof the WD, while keeping the fall in pressure before the final pressurereducing system to no more than 10%.

6.15 Except for vertical rises between floors or at intermediate points onlong runs, the pipework should have a continuous fall such that anycondensate flows by gravity in the same direction as the steam. Air vents andsteam traps should be fitted at each vertical rise.

6.16 The condensate discharge system should be sized to ensure that thehigh volume of condensate found during the initial stages of heating can bedischarged without “water-logging” the heat exchanger.

6.17 When the steam supply pressure at the inlet to the WD exceeds themaximum value specified by the manufacturer, a pressure reducing valveshould be fitted to the supply pipe at least 3m from the WD.

6.18 Careful attention should be paid to the siting of all pressure reliefvalves to ensure that the WD is properly protected.

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6.19 Relief valves and their discharge pipes should be large enough toprevent the pressure in the supply pipes rising to more than 10% above thedesign pressure for the heat exchanger. The discharge pipe should terminate ina safe position outside the building.

6.20 Steel and copper piping traditionally used for steam supply areacceptable for this application.

6.21 Excessive moisture in the steam supply will impair the heating efficiencyof the heat exchanger.

Steam for direct heating

6.22 Steam for direct heating should meet the requirements described abovebut should also be of an appropriate chemical and microbiological quality.

6.23 Any contaminants carried with the steam supply will be transferred tothe load being processed either through contact with water which was steamheated or directly.

6.24 Filming amines or similar volatile corrosion inhibitors used to preventcorrosion in condensate return pipes should not be employed in steam usedfor direct heating.

6.25 The quality of steam required will depend on the nature of the load tobe processed and, in particular, on the intended use of the load items. Inheating for loads intended for use in surgically invasive procedures, thecondensed steam should meet the chemical purity Standards specified forWater for Irrigation EP and should contain no more than 0.25 Endotoxinunits/ml. Detailed guidance is given in HTM 2031 ‘Steam for sterilization’ andthe same Standards are applicable.

6.26 When direct heating of the load by steam is used, the design of theWD should include adequate venting to the chamber to ensure that there is nopossibility of pressurisation during a single fault condition.

Integral steam generators

6.27 Some WDs are equipped with small electrically heated steamgenerators to raise steam to heat the load directly by thermal disinfection.

6.28 They may be of the “open-boiler” type which are so designed andconstructed that they are unable to generate an internal pressure aboveatmospheric pressure. The design should ensure that, under a single faultcondition eg obstruction of the steam discharge port, the boiler cannotbecome pressurised.

6.29 Integral steam generators which are pressure vessels should complywith the requirements of BS 5500: 1994.

Condensate recovery

6.30 Condensate from steam heating systems (calorifiers, dryers) and steamtraps on the pipeline is suitable for recovery and should be returned to thesteam generating plant when recovery is economically justifiable.

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Compressed air

6.31 A compressed air supply may be required for the operation of controlsand also for air drying. When the WD does not contain an integral aircompressor (see paragraph 4.46) the air may be supplied from a piped service(mains supply) or from a local compressor.

Mains supply

6.32 If air is supplied by pipeline from a central air-compressor system apressure gauge of the Bourdon type, complying with EN 837, should be fittedon the supply line to the WD via an isolation valve.

6.33 A reducing valve, or other automatic device, should be fitted to reducethe pressure of air delivered to the WD to no more than the maximum supplypressure specified by the manufacturer. A pressure relief valve will normally berequired.

Local compressor

6.34 When it is not practical to obtain compressed air from a mains supply,a dedicated compressed air system should be installed to supply the WDs.

6.35 The compressors may be too noisy to install with the WD and mayneed to be located in a dedicated location away from noise sensitive areas.

6.36 Components of the compressed air system which require servicing andmaintenance, such as dryers and filters, should be located where they arereadily accessible for service or exchange.

Air quality

6.37 The quality of air may be critical for some applications and some WDswill incorporate appropriate filters. When the purchaser is to be responsiblefor the provision of filtered air the TP(S) should ensure that the quality of airavailable meets the WD manufacturer’s specification or the requirementsgiven below.

6.38 Air that could come into direct contact with the load, such as air usedfor drying the load or testing the free-passage of lumens, should be oil-free (ieshould have no more than 0.5mg of oil per cubic metre of free air measuredat 1013 mbar and 20°C; see ISO 554), be filtered to an efficiency of at least95% when tested in accordance with BS 3928 and be free of bacteria (seeHTM 2022 ‘Medical gas pipeline systems’).

6.39 Air for control purposes should be free of liquid water, filtered to 25 µm (5 µm for precision controls) and lubricated with micro-fog oil particlesof 2 µm or less.

Drainage

6.40 All effluent from a WD is potentially contaminated and should bedisposed of to the main drain.

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6.41 Effluent may originate from each of the stages of the process whichmay include:

a. flushing to remove gross contamination;

b. washing with detergent and/or enzymatic cleaners;

c. rinsing, with or without the addition of a neutraliser, rinse aid orinstrument lubricant;

d. chemical disinfection or thermal disinfection;

e. post-disinfection rinsing;

f. drying.

6.42 Effluent from the initial stages [(a) and (b) above] of the process maycontain significant concentrations of organic contaminants and potentiallyinfective micro-organisms. Effluent from the middle stages [(b), (c) and (d)above] may contain some organic contaminants and potentially infective micro-organisms and high concentrations of process chemicals. Effluent from thelatter stages [(d), (e) and (f) above] may be at high temperatures (90–100°C).

6.43 Effluent from WDs (other than WDs for human-waste containers)should pass via an air break into a tundish or tank before being dischargedto drain. The air break should be preserved at all times to prevent the WDand its associated pipework being contaminated by reverse flow from thedrainage system.

6.44 When a tank supplies water to a pump on the WD, the overflowdischarge from the tank should also include an air break.

6.45 The drainage system from the installation should be trapped anddesigned to pass the flow rate of water, air and condensed steam specified bythe manufacturer, with account taken of the peak output during the operatingcycle.

6.46 The drainage system should be designed to pass and maintain insuspension the solids removed from the load during the flushing process. Theminimum diameter of the drainage system should be greater than themaximum diameter of the most restricted section of the discharge from theWD chamber.

6.47 Means shall be provided to prevent, as far as possible, flash steambeing liberated into the atmosphere or causing condensation on electricalequipment.

6.48 The discharge temperature from a WD may be as high as 95°C. Thematerials used for the construction of the discharge system should be chosento withstand temperatures up to 100°C.

6.49 Attention is drawn to the legal requirement (Public Health Act 1936,Paragraph 27) that the maximum temperature of any liquid to be emptied intothe public sewer or communicating drain is 43°C. This should be interpreted asreferring to the main building connection to the sewer and not to the internalbuilding drain.

Hazardous effluents

6.50 The discharge of soil from WDs should be regarded as being no more,but no less, hazardous than the discharge from any other sanitary appliance ega WC.

WDs for human-waste containers areconnected directly to a soil pipe butare tested to ensure that backsiphoning cannot occur under severeoperating pressure.

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6.51 The discharge of process chemicals, including detergents andmicrobicides, may require special attention. The local water undertakingshould be consulted before such chemicals are discharged into the drainagesystem as it may be necessary to neutralise or inactivate them beforedischarge.

6.52 A sealed and vented drain should be used for the discharge ofchemicals with a significant vapour pressure – determined at the maximumattainable temperature of effluent in the drain – which may be hazardous tohealth or a nuisance. Possible backflow from the drain should be prevented bythe inclusion of a check valve and a vacuum breaker.

6.53 WDs should not be used to process items known to be contaminatedwith high titre pathogens in Hazard Group 3, eg arising from researchactivities, or any pathogens in Hazard Group 4 unless the items have beensterilized by an appropriate steam sterilization cycle in a laboratory sterilizerdesigned and operated for the purpose (Further guidance is given in HTM2010 and advice should also be sought from the HSE).

Ventilation

6.54 Ventilation of the area near WDs may be needed to remove excessiveheat and humidity, and also vapours from disinfectants such asglutaraldehyde.

6.55 General room ventilation will be sufficient for most WDs, but localexhaust ventilation may be required for chemical disinfection/sterilizationsystems.

6.56 Electrical systems used in ventilation systems should take account ofthe high levels of humidity that may be discharged and the potential for thisto condense within the ventilation system.

6.57 All ventilation systems should meet the ventilation requirements of theWorkplace (Health, Safety and Welfare) Regulations 1992.

6.58 Further guidance on ventilation systems may be found in HTM 2025‘Ventilation in healthcare premises’.

General room ventilation

6.59 WDs for most healthcare applications do not require a filtered airsupply in the room in which they are located unless there is no physicalsegregation between this area and the packing/sterilizing area.

6.60 The ventilation system in the area of a WD used to decontaminateused items should be a “full fresh air” system without recirculation. Indesigning the ventilation system reference should be made to HTM 2025‘Ventilation in healthcare premises – Design considerations’.

6.61 Decontamination areas should generally be at a pressure belowatmospheric; a 5–10Pa pressure difference is sufficient to minimise thedispersion of potentially infective aerosols into adjacent areas.

6.62 In designing the ventilation system two factors are of particularimportance:

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• the provision of adequate cooling so that working conditions remaincomfortable for staff;

• correct sizing of the room ventilation system and/or interlocking withextract fans on WDs and other extraction systems in the area to ensurecorrect operation of both the room ventilation system and themachine/process specific extraction system(s) when extraction fans onWDs and/or extraction hoods are in operation.

6.63 WDs, particularly those employing thermal disinfection processes and adrying stage, may discharge significant heat energy to the surroundingenvironment. In designing a ventilation system for single ended WDs, accountshould also be taken of the heat emitted from the load after it has beenremoved from the WD.

6.64 Current experience suggests that a 250 litre capacity cabinet WD, witha thermal disinfection stage and hot air drying installed as a free standing unitwith the door closed and the machine operating, will release by radiation andconvection approximately 1.0 kW of heat energy. A full load of processeditems being removed from the WD will release approximately a further 0.5 kW.

Machine ventilation

6.65 WDs are often run under a slight negative pressure to minimise thepotential for the discharge of aerosols into the environment.

6.66 WDs not equipped with an air extract system may require siting underan extraction hood. The capture velocity in the vicinity of the process should bewithin the range 0.25–0.5m/s to ensure adequate extraction of steam andwater vapour.

6.67 The extracted air from WDs is discharged into the atmosphere. In largeinstallations significant quantities of useful energy may be discharged as aresult. A heat recovery system may be economically viable and a fullassessment of the benefits and costs should be carried out. Additionalguidance is given in HTM 2025 Volume 2 ‘Ventilation in healthcare premises –Design considerations’.

6.68 The air extracted from WDs, both during the washing and the dryingphases of an operating cycle, will normally have a high moisture level. Theextraction system should, therefore, be equipped with a drain to discharge thecondensate and should be designed and constructed so that it may be cleanedperiodically. The drainage system should be constructed with a continuous fallto discharge, without any upstand at the point of connection to the ventilationsystem to prevent pooling.

6.69 The extraction system should be constructed from corrosion resistantmaterials. The discharge from some WD dryer systems is at high temperature(≥105°C) which is sufficient to melt or distort some lightweight plastic ductingmaterials. Typical worst case values are temperatures >105°C and 100%saturation.

6.70 Current experience suggests that flow rates for built-in extractionsystems are in the order of 100 m3/hr for a single cabinet 250 litre capacitymachine, and up to 800 m3/hr for a multi-cabinet continuous process machineof 1500 litre total capacity (ie three 500 litre chambers).

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6.71 The output from the extraction system should be considered aspotentially containing infective aerosols and should, therefore, be dischargedaway from opened windows, air intake systems or where down draughtsoccur. It is important that adequate dispersal is achieved and roof-leveldischarge is preferred.

6.72 The extraction ductwork connected to the WD is an efficienttransmission system for noise originating within either the WD or extractionplant. Care is needed in the design and construction of the ducting to ensurethat noise does not become a problem. This may require the use of soundattenuators as part of the ductwork design. Additional guidance is given inHTM 2025 Volume 2 ‘Ventilation in healthcare premises – Designconsiderations’.

6.73 Extraction hoods to protect operators against aerosol dispersion ofpotentially infective material, eg over a manual washing sink or an unliddedultrasonic bath, should have extraction velocities at working level of no lessthan 0.7–1.0 m/s.

6.74 Extraction systems, eg bench extraction ventilation designed to protectoperators against contact with vapours or gases such as those arising fromchemical microbicides including glutaraldehyde, should have extractionvelocities of 5.0–6 0 m/s.

6.75 Extraction hoods should be provided with local controls, or a controlsystem interlocked with the equipment with which they are intended to work,so that they may be shut down when not required.

6.76 Purpose built work stations for glutaraldehyde disinfection/sterilizationwith built-in ventilation systems are also available. These are generally installedin a similar manner to laboratory fume cupboards (see BS 5728: 1990).

6.77 Extract from WDs and extraction hoods should not be dischargedthrough general ventilation extraction systems. The extract from two or moreWDs and/or extraction hoods should not use common ducting unlessprovision is made to ensure that there is no risk of contamination of adisinfected load from the cross-connection.

Chemical additives

6.78 Safe storage provision is needed for containers of chemical additivesused in the WD. These chemicals are frequently corrosive, irritant and toxicand provision should be made in, or adjacent to, the storage area for anemergency eye wash station and a source of running water to dilute anyspillage.

6.79 In large installations with two or more Type 2 machines, as may oftenbe required in SSDs, bulk storage tanks for chemical additives required for theprocess may be preferred with a piped distribution system to each WD.

6.80 For each chemical additive to be used there should be two storagetanks in parallel, one of which may be a small reserve tank, to permit cleaningand maintenance of the system without interrupting the use of the WDs, tofacilitate segregation between separate batches of chemical additive and toallow for an orderly change to a different formulation if required.

Although higher velocities will notimpair extraction they are wastefulof energy.

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6.81 The liquid concentrates are often viscous and chemically aggressive. Thepipework, valves etc used for the distribution of these chemicals will need towithstand the corrosive effects of these materials. Advice should be soughtfrom the manufacturer of the chemical additives on suitable materials,construction and pumping systems for the distribution system.

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7.0 Water supply

7.1 The number, nature and quality of water supplies required aredependent on the size and type of WD.

7.2 WDs may be supplied with both hot and cold water. When hot wateris required as part of the operating cycle, it is generally advantageous tosupply hot water to the WD rather than heat cold water to the requiredtemperature within the WD.

7.3 The quality of water used at all stages in the decontamination processis critical to the successful outcome of the process.

7.4 At each stage the water quality should be compatible with:

• the materials of construction of the WD;

• the load items to be processed;

• the chemical additive used;

• the process requirements of that particular stage.

7.5 The key factors are:

• hardness;

• temperature;

• ionic contaminants (eg heavy metals, halides, phosphates and silicates);

• microbial population;

• bacterial endotoxins.

Water hardness

7.6 Hard water is caused by the presence of dissolved salts of the alkalineearth (calcium, magnesium and strontium) which come out of solution anddeposit as hard mineral layers (lime-scale) when water is heated orevaporated.

7.7 The fouling of electrical heating elements or heat exchangecomponents by hard water dramatically reduces the heat-transfer efficiencyand can quickly lead to an increase in heating costs of 50–100%.

7.8 The deposition of lime-scale within pipes and around the edges ofspray nozzles will seriously impair the performance of a WD. Hard water willcause scaling on the edges of spray nozzles even when fed with only coldwater.

7.9 The presence of hardness in water seriously impairs the efficiency ofmost detergents and disinfectants. If the use of hard water is unavoidable itwill be essential to use process chemicals that contain sequestering agents.This adds considerably to the cost of the process.

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7.10 Using hard water in the thermal disinfection and final rinse stages ofthe WD cycle is one of the major causes of white powdery deposits on loaditems. These are not only unsightly and an unwelcome contaminant but act asa focus for soiling and recontamination of the item in use. In some applications(eg with optical systems) such deposits may seriously impair the utility of theitem.

7.11 Most WDs will operate with water of hardness values up to 125mg/lCaCO3 but are more effective and cheaper to operate when the hardness ofthe water does not exceed 50 mg/l CaCO3.

7.12 Some WDs are fitted with integral water treatment systems (seeparagraphs 7.31 to 7.33).

7.13 The temperature at which water is supplied to each stage of theprocess has a major effect on the efficacy of the process.

7.14 Water at too high a temperature during the initial flushing stage maylead to the coagulation of proteins and thus serve to “fix” proteinaceous soilto the surface of the load items. The British Standard (BS 2745) recommendsthat the initial temperature should not exceed 35°C. The initial flushing stageshould be supplied with water from a cold supply.

7.15 Water at too low a temperature during the washing stage of the cyclewill often impair the ability of detergents used to remove soils composedlargely of fats, oils or grease.

7.16 When enzymic cleaners are used the water temperature must bemaintained close to the optimum temperature specified by the manufacturer;too high a temperature will inactivate the enzymes.

7.17 When chemical disinfectants are used the rate of activity generallyincreases with increased temperature. Too low a temperature will cause failureto attain the required microbial activation. However, too high a temperaturewith particular compounds can lead to degradation of the active components,evolution of toxic vapours or adverse reactions with the load items beingprocessed.

7.18 The maximum temperature of rinsing water must be compatible withthe items being processed; many items used in medical practice aretemperature sensitive or may be damaged by thermal shock.

Ionic contaminants

7.19 Water used in the cleaning and disinfection of stainless steelinstruments should have a chloride concentration between 0 and 120 mg/l Cl–

to avoid the risk of corrosion. Chloride concentrations greater than 240 mg/lCl– cause pitting to occur.

7.20 Tarnishing of stainless steel instruments, shown by blue, brown oriridescent surface coloration, occurs when heavy metal ions – such as iron,manganese or copper – are present in the process water. In hot water (over75°C) magnesium ions and silicates can cause similar discoloration.

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7.0 Water supply

Microbial population

7.21 The purpose of the decontamination process is to remove soiling andreduce the microbial contamination to an acceptable level for the intendeduse of the items to be processed. The water used at each stage of the WDprocess cycle should not increase the bioburden of the load items.

7.22 For items which are intended to be used without furtherdecontamination processing (eg terminal sterilization) the nature and extent ofthe microbial population in the final rinse water should not present a potentialhazard to the patient, either through infection or by leading to a erroneousdiagnosis. Appropriate treatment to control or reduce the microbialcontamination in water may be required.

Bacterial endotoxins

7.23 Bacterial endotoxins are thermostable compounds derived from the cellwalls of bacteria which, when introduced into the human body, can cause afever-like reaction and other adverse effects (for a more detailed explanationsee HTM 2010 ‘Sterilization’, Volume 5). They are not readily inactivated atthe temperatures used for disinfection or sterilization.

7.24 Water used for the final stages of processing in a WD, where there is asignificant risk of residual water remaining on the load items, should notcontain more than 0.25EU/ml when the WD is being used to process surgicallyinvasive items or those which are intended to come into contact withparenteral solutions.

Water treatment

7.25 Despite the cost involved in treating water from the public supply toprovide the optimum quality for use at each stage in the WD process cycle,this is usually cost-effective.

Chemical purity

7.26 There are generally four methods of water treatment available for useon water supplies to be used in WDs:

• water softeners;

• water de-ionisers;

• distillation;

• reverse osmosis.

Water softeners

7.27 Water softeners, or “base-exchange” softeners, consist of an ion-exchange column containing a strong cation resin in the sodium form.Calcium and magnesium ions in the water are replaced by sodium ions. Thecolumn may be regenerated by treatment with a solution of common salt(sodium chloride).

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7.0 Water supply

Table 4 Use to which water of various qualities may be put

Types of water Application

Cold water Flushing ie removal of gross soiling

Potable water Flushing/cleaning

– soft Cleaning with detergent or enzymaticeg < 50mg/l CaCO3 cleaners

Thermal disinfection in WDs for human-waste containersFinal rinse water in WDs for human-wastecontainers

– hard Flushing for WDs for human-wasteeg >125mg/l CaCO3 containers will require use of

descalers

Softened water Desirable in all water > 50mg/l CaCO3-based exchange Essential in all water > 125mg/l CaCO3softener for use in WDs

Purified water Final rinse water for laboratory WDs

De-ionised water Thermal disinfection in all WDsFinal rinse water

Reverse osmosis Diluent for chemical disinfectionFinal rinse water

RO/0.22 µm filtered Post-disinfection/sterilizationrecirculated, heated rinsing of products intended and or UV disinfected for immediate use in critical

applications eg fibre-opticendoscopes

Sterile purified water Post-disinfection/sterilizationrinsing of products intended forimmediate use in critical applications eg fibre-optic endoscopes

Note: The above table shows suitable applications for the various qualities ofwater commonly available. Although water of lower quality may be used, thiswill normally require additional chemical additives and may entail someimpairment of the WD performance.

7.28 The concentration of total dissolved solids in the water is not reducedby this process. The sodium salts which remain do not readily form harddeposits to foul heat exchangers or spray nozzles but if used as the final rinsewill leave white deposits on the load items as they dry.

7.29 The process is simple to operate with an automated in-line system, willhandle water with varying levels of hardness, and is simple and safe toregenerate. After regeneration, however, high levels of chloride ions may bepresent in the initial output from the softener which should be run to waste.

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7.0 Water supply

7.30 In common with other water treatment systems, the base-exchangesoftener needs to run to a minimum volume of out-flow if the required waterquality is to be achieved. This volume should be specified by the manufacturerof the treatment plant. The output from the softener should be to a watertank and the volume demanded each time additional water is fed to the tankshould exceed the minimum flow.

Integral water softener

7.31 WDs are available with built in base-exchange water softenersalthough these are generally laboratory WDs.

7.32 Water softeners should be chosen based on the total demand ofsoftened water in the unit eg SSD including when necessary provision formanual washing facilities and other plant.

7.33 Base-exchange softeners may cause a significant increase in themicrobial content of the water.

De-ionisers

7.34 De-ionisation or demineralisation systems can remove virtually all thedissolved ionic material by ion-exchange using a combination of cation andanion exchange resins either in a single column (mixed bed) or in a separatecolumn.

7.35 Operating costs of mixed bed de-ionisers are usually higher than fortwo-stage systems.

7.36 Systems are available in a range of sizes from small wall-mounted unitsin which ion-exchange resins are contained in disposable cartridges to largeindustrial units. Regeneration requires the use of strong acid (hydrochloricacid) and strong alkali (sodium hydroxide). For most types of installation anexchange column service is available from the water treatment suppliers.

7.37 De-ionised water may be heavily contaminated with micro-organismsand de-ionised water will be colonised rapidly because the chloride ionsnormally present to control microbial growth have been removed. De-ionisedwater should not be used for the final rinse of products intended for invasiveuse without further decontamination processing by heating, filtration etc (seebelow).

7.38 For a given output volume, the initial cost of providing de-ionisationequipment will be lower than for reverse osmosis (RO). However, theinconvenience and cost of the regeneration process for de-ionisers, and thebetter microbial quality of the RO process, makes RO the preferred option.

Reverse osmosis (RO)

7.39 RO treatment plants remove dissolved contaminants from water bypassing the water, under pressure, through a semi-permeable membraneagainst an osmotic gradient. The process will remove organic material,bacterial endotoxins and micro-organisms, as well as ionic species.

7.40 The initial capital cost of an RO plant is generally higher than for a de-ionisation system supplying a similar volume of water but operational costsare generally lower. When appropriate measures are taken to maintain the

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7.0 Water supply

microbial quality of the water during storage and distribution, the water isendotoxin-free and has a negligible microbial population.

Distilled water

7.41 Distilled water may equal or exceed the purity of RO water but, despitethe relatively low capital cost of the necessary plant, is very expensive toproduce due to the high energy usage.

7.42 Distilled water is only used in laboratory WDs and RO is usually anacceptable alternative.

7.43 When indirect steam heating of WD water tanks and air dryers takesplace, the condensate formed may provide an acceptable quality of water foruse instead of distilled water.

Microbial purity

7.44 Potable water from the public supply has a low microbial content andshould be free from pathogenic organisms, other than those which may causeopportunistic infections in immunologically compromised patients.

7.45 On storage in tanks and cisterns, the microbial content may increaseconsiderably.

7.46 Attention is drawn to the requirement under the code of practice forcontrol of legionella that water in intercepting tanks must be stored below20°C or above 55°C.

7.47 The extent and nature of microbial contamination in the water suppliedto a WD will depend on the stage in the process cycle at which it is to be usedand the intended use of the decontaminated load at the end of the process.

7.48 Water stored at 60°C or above may be assumed not to have aproliferating microbial population.

7.49 When sterile water is required for final rinsing in critical applications, egWDs for endoscopes, this should be provided by using a single-use containerof sterile water for each cycle whenever practicable. The pipework, valves andpumps through which the water will pass should be subjected to anappropriate sterilization/disinfection process.

7.50 When water is treated by filtration, eg through a 0.22 mm filter toremove microbial contaminants, rigorous controls are needed to ensure thatthe system works effectively. This should include:

• either maintaining the pressure drop across the filter throughout itsworking life – a decrease in differential pressure being cause forrejection of the process cycle and a change of filter – or, a bubble pointtest before and after each process cycle (see BS 1752: 1983);

• a continuous recirculation system so that the filter is not left wet in staticwater;

• treatment of the circulating water to ensure that proliferation ofmicrobial contamination is inhibited either by use of elevatedtemperature (eg >60°C) or by the use of UV irradiation (wavelength 260 ± 10nm; >2J. m–2).

(See also report of the Expert Advisory Committee on biocides).

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7.0 Water supply

Pipework

7.51 The pipework used to supply the various grades of water should beappropriate to the quality of water carried. Sterilized uPVC or stainless steelpipes are preferred for all qualities of purified water.

7.52 All pipework should be run with a continuous fall to the dischargepoint so that it is free draining. It should be free from dead ends and otherareas where water may become stagnant.

Water supply bylaws

7.53 All the organisations responsible for water supply within the UK havethe statutory power to make, and the duty to enforce, bye-laws (Regulationsin Northern Ireland) for the prevention of waste, undue consumption, misuseor contamination of the water supplied by them. The Model Water Bye-laws1986 form the basis of these bye-laws (Regulations).

7.54 Attention is drawn to the following points:

• Bye-laws 38 to 41 require storage cisterns to be fitted with warningpipes (and an overflow if in excess of 1000 litre capacity). The warningpipe and overflow should not comprise, or have connected to it, aflexible hose.

• Byelaw 25 Schedule A gives examples of points of use or delivery ofwater where backflow is, or is likely to be, harmful to health due to asubstance continuously or frequently present (Byelaw 25 (1)(a)).

• This schedule lists inter alia water softening treatment plant, bedpanwashers, bottle washers, dishwashers and disinfection equipment andclearly applies to all WDs.

• The required protection is a Type A air gap at the point of use or aninterposed cistern.

• Water softeners, regenerated only by means of sodium chloridesolutions, need only be protected by a Type B air gap.

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7.0 Water supply

8.0 Chemical additives (detergents, enzymic cleaners,rinse aids, lubricants and disinfectants)

Introduction

8.1 Chemical additives are not necessary for all applications while they mayenhance the removal efficacy they then in turn have to be removed during therinsing stage. For applications in the laboratory and in the preparation ofcomponents and equipment used in manufacturing medical devices andmedicinal products, it may be better not to use chemical additives when theiruse is not essential. Further guidance is given in the chapter on each type ofWD.

8.2 In choosing the various chemical additives which may be required foreffective cleaning and disinfection, it is important to ensure that theformulation of each chemical additive is compatible with:

• the materials of construction of the WD;

• the process being operated in the WD;

• the quality of water available;

• the items to be processed and their intended use;

• any other additives to be used in the WD process;

• any intended subsequent decontamination process (eg sterilization).

It is also important that the required concentration can be accurately andreproducibly generated by the dosing system(s) on the WD.

Compatibility with the materials of construction of

the washer-disinfector

8.3 The pH, redox potential and ionic nature of the chemical additive isimportant in determining whether it will cause corrosion or electrolytic attack(either between different materials in the WD or between the WD and items inthe load).

8.4 Chemical additives which can be absorbed into, or adsorbed onto,surfaces of the WD (eg plastic pipework) may be carried over into subsequentstages of the process (see also paragraphs 8.7 and 8.15).

Compatibility with the process

8.5 The performance of the additive must be matched to the physicalcharacteristics of the operating cycle, eg jet washing action systems requirelow foam detergents, if the washing action is not to be impaired.

Compatibility with the items to be processed

8.6 The chemical additives used must be compatible with the materials ofwhich the load items are constructed and should not cause chemical or

The precise formulation of thechemical additive will affect itscompatibility; it is not sufficient todetermine only the compatibility ofthe principal active constituents

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physical damage – eg phenolic compounds used in detergents anddisinfectants may cause material changes in rubber and plastics, while theanodic coating on the surface of anodised aluminium is removed by stronglyacid or strongly alkaline compounds.

8.7 The chemical additives used must be readily removed from the loaditems by rinsing with water and should be biologically compatible with theintended use of the load items. Chemical additives which are intended topersist on the surface of items processed through the WD (eg lubricants)should be biologically compatible with the intended use of the load items.

Compatibility with the quality of water

8.8 Many detergents and disinfectants are seriously impaired in theiractivity by hard water. If only hard water is available formulations should besought which are intended for use with water of that quality.

8.9 Detergent formulations intended for use only with soft water may giverise to precipitation if used with hard water, particularly at elevatedtemperatures. Once this precipitation has occurred on the surfaces of the WDor the load it is particularly difficult to remove (see paragraph 8.7).

Compatibility with other chemical additives

8.10 Many of the chemical additives which might be used are incompatiblewith one another – eg quaternary ammonium compounds which are oftenused as surfactants will rapidly destroy the activity of enzymic cleaners, whilemany detergents will inactivate chemical disinfectants.

8.11 The additives used should be both compatible with other chemicalsused in the same process stage and, as far as may be practicable, with thoseused in preceding and subsequent stages to minimise the adverse effect ofany carryover.

Compatibility with subsequent decontamination

processes

8.12 Chemical additives which may persist on the surface of itemsprocessed through the WD should be compatible with any subsequentdecontamination process which may be required, such as terminalsterilization. An in-process instrument lubricant which deposits a lubricant filmon all surfaces of the instrument should only be used if it has beendemonstrated to be compatible with any subsequent sterilization process.

General

8.13 In almost all cases, attainment of the specified concentration ofchemical additives is essential to effective processing. The addition of too littlewill impair the process while too much is wasteful, may also impair theprocess and may contribute to unacceptably high residual levels.

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8.0 Chemical additives (detergents, enzymic cleaners, rinse aids, lubricants and disinfectants)

8.14 Suppliers of chemical additives should provide product data sheets andmaterial safety data sheets for the products supplied. These should includedetails of biocompatibility studies.

8.15 Suppliers of chemical additives should provide details of the analyticalmethods which may be use to detect residual concentrations of product. Thesensitivity of the method should be sufficient to determine the presence of thecompound below the level at which any adverse biological reaction may bedetermined.

Detergents

8.16 For most applications, mild alkaline detergents in the pH range8.0–11.0 are preferred. Alkalinity improves the efficacy of detergents both byenhancing their inherent cleaning capabilities – neutralising and helping toremove acid soils, emulsifying oils and fats and peptidising proteins – and bysynergistic action with other detergent compounds. Many surfactants workbetter in the presence of alkaline “builders” such as sodium tripolyphosphate(STPP).

8.17 Alkaline detergents inhibit the growth of most micro-organisms.Alkaline detergent residues are readily detected by pH measurement.

8.18 Acid-based detergents should only be used for stainless steel surfacesand then only for limited applications, eg for de-scaling instruments that havebeen processed in hard water.

8.19 Cleaning agents for use in WDs should be:

• liquid – to facilitate accurate dispensing;

• non-abrasive;

• low foaming;

• free rinsing;

• biodegradable.

8.20 Cleaning agents should not contain:

• artificial colouring agents;

• optical brighteners;

• perfumes;

• halides at an in-use concentration greater than 120mg/l;

• fatty soaps, glycerine or lanolin.

Enzymic cleaners

8.21 Enzymes are organic catalysts through which the normal metabolism ofmost living organisms takes place. Although produced by living organisms theyare not themselves alive. Enzymes are large organic molecules whose stericconfiguration (shape) affords them the ability to catalyse many reactions in theliving cell.

8.22 Enzymes are classified into groups depending on the nature of thechemical reaction that they catalyse. Generally the enzymes used in enzymic

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cleaners are hydrolases ie they promote the hydrolysis of the substrate withwhich they interact.

8.23 Enzymic cleaners are themselves proteins (often derived from thebacteria B subtilis and B stearothermophilus) and may be sensitising orallergenic agents. A similar adverse reaction is allegedly produced in somepeople by domestic biological washing powders.

8.24 Many of the developments in enzymic cleaners originated with thepre-soak cleaners and subsequently the biological washing powders used indomestic laundry applications.

8.25 A considerable proportion of the soiling found on medical itemscontains proteins which act as binding agents. Particulate dirt can be boundby the coagulation of these proteins on the surface.

8.26 If the binder proteins can be broken down into a simpler molecularform this binding action is destroyed and the bound soil, as well as theprotein, can be released from the surface.

8.27 Formulations will often include buffering agents to maintain the pHwithin the preferred range. Most enzymes have an optimum pH at which theiractivity is greatest and a pH at which the enzyme itself is most resistant tothermal degradation, although these two values are not necessarily the same.

8.28 For example the proteolytic hydrolase derived from B subtilis, subtilisinA, withstands temperatures up to 60°C and displays its greater stability at pH 9.4.

8.29 The importance of the enzymic solution being at the correcttemperature and pH, as well as being used for the specified contact time,cannot be too strongly emphasised.

8.30 Enzymes are not themselves cleansing agents. A properly balanceddetergent may still be needed to remove the simpler molecular forms resultingfrom the enzymic action.

8.31 It is important to ensure that any detergents used are compatible withthe enzymes – quaternary ammonium compounds (QACs) deactivate many ofthese enzymes (the deactivation of enzymes in the bacterial cell is one of theproposed mechanisms of action for the microbicidal action of QACs).

8.32 Enzymic formulations for cleaning solid surfaces are available in twoforms:

• a pre-soak formulation which is used to digest proteinaceous soil and isthen followed by normal washing process using detergent;

• a combined enzyme and detergent formulation.

Cleaning additives for ultrasonic cleaners

8.33 Only detergents specifically intended for use in ultrasonic cleanersshould be used. The use of other detergents may impair rather than enhancethe cleaning process.

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Rinse aids

8.34 Rinse aids are generally formulated from surfactants and are designedto make the water more free rinsing. They are often at low pH in order toremove deposited salts arising from the use of hard water.

Lubricants

8.35 The addition of oil-based compounds to the cleaning process is wrongin principle. They deliberately cause contamination over the entire cleanedsurface. If they are to be used the water-soluble type should be used. Mineraloils have poor biocompatibility and may inhibit the penetration of steam orsterilant gases on terminally sterilized product.

8.36 Lubrication should only be applied to those areas where it is requiredduring the inspection/packing process after thorough cleaning of theinstrument.

Disinfectants and/or sterilants

Choice of disinfection method

8.37 Thermal disinfection using moist heat is the preferred method andshould be used whenever it is compatible with the load to be processed.

8.38 Temperatures in excess of 65°C and up to 95°C (or in some cases100°C) can be used for disinfection; the lower the temperature the longer theexposure time in order to obtain the same reduction in microbial population.The thermal disinfection process is reliable, reproducible, free from toxicresidues and capable of easy and economical physical monitoring andrecording.

8.39 Chemical disinfection should only be used for products which cannotbe treated using thermal disinfection methods.

Criteria for selecting a chemical disinfectant

8.40 Chemical disinfectants differ in their ability to kill micro-organisms.

8.41 In order to choose a disinfectant for a particular application it isnecessary to know the microbicidal activity required – both the number andtypes of organisms that may be encountered and the assurance that may berequired that they have been inactivated. The technical information from themanufacturer of disinfectants should provide the required information aboutthe activity of the product.

8.42 The major application for chemical disinfection is in processing for re-use thermolabile equipment such as fibre-optic endoscopes. Two distinctstandards are applicable: for those instruments that will only come in contactwith intact mucosa; and for those that will invade a sterile body space. Whilethe same or similar disinfectant formulations may be used for both applicationsthe operational controls required may be different. This is addressed in Chapter 12. Further guidance is given also in HTM 2030 ‘Validation andverification’.

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8.43 Although there are numerous disinfectant formulations available onthe market, there are relatively few generic types of disinfectant suitable forchemical disinfection in WDs.

8.44 A solution containing 2% glutaraldehyde is the most commonly useddisinfectant. Other aldehydes, quaternary ammonium compounds, hydrogenperoxide, peracetic acid, chlorine dioxide and alcohol solutions have also beenrecommended by various workers and may have particular benefits in certainapplications.

8.45 The guidelines from various professional bodies are not in agreementas to the disinfectant contact time to be used and few recognise the need tospecify the temperature or minimum concentration. Furthermore, theseguidelines may not be in accord with the recommendations from themanufacturer of the item to be sterilized or from the manufacturer of thedisinfectant.

8.46 Current guidelines from the UK Departments of Health are given inHealth Circular HC (91)33. These recommend:

• a freshly activated solution containing 2% glutaraldehyde at roomtemperature for 30 minutes for dealing with contamination with HIV orHBV;

• a 2% solution of glutaraldehyde for 60 minutes if mycobacterialcontamination is suspected.

8.47 ‘Guidance for Clinical Health Care Workers: Protection againstinfection from HIV and hepatitis virus’ produced by the Expert Advisory Groupon AIDS also recommends “endoscopes which will enter sterile body cavitiesmust be immersed for a minimum of three hours”.

8.48 While these times may be reduced if the items are processed in avalidated automatic WD with appropriate routine monitoring, the exposuretime should in all cases be at least that specified by the disinfectantmanufacturer. More detailed information is provided in HTM 2030 ‘Validationand verification’.

8.49 Instructions for use supplied with the disinfectant should include:

• the quality of water with which the product should be diluted;

• the storage life – the life before dilution or activation (or before use ifsupplied at the required concentration for use);

• the use-life – the storage life after dilution and storage under statedconditions within which the unused disinfectant will retain activity at, orabove, the minimum specified by the manufacturer;

• the re-use life – the extent to which the disinfectant may be re-used.This may be specified as time, the number of load items processed orthe number of disinfection cycles.

Materials compatibility

8.50 The disinfectant should not cause damage to either load items or theWD in which it is used. Damage which may occur with incompatibledisinfectants includes corrosion, embrittlement or swelling of plastics,degradation of lens cement in optical systems etc. The potential forelectrolytic attack to occur as a result of different metals in the load and theWD coming into contact, via a powerful electrolyte, should not be overlooked.

This is event related not timerelated but when a manufacturerspecifies a “use-life” this should bebased on simulated “worst case”use conditions.Whenever possible, a single use ispreferred since it avoids the manyproblems associated with controlof re-use

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8.51 The material of construction of the WD and of the items in the loadshould not inhibit the disinfectant.

Safety of disinfectants

8.52 Many of the compounds which are most effective as disinfectants arepotentially human health hazards. Employers are required by law to doeverything that is reasonably practicable to protect the health of their workers.The safe use of these compounds is covered by the COSHH Regulations.

8.53 Glutaraldehyde has an occupational exposure standard of 0.2 ppm overa 15 minute reference period. This should not be regarded as a permissiblelimit but as a maximum which should not be exceeded. Further guidance isgiven in HTM 2030 ‘Validation and verification’.

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9.0 Washer-disinfectors for human-waste containers

Introduction

9.1 This chapter discusses specifications for WDs intended for emptying,cleaning and disinfecting human-waste containers.

9.2 WDs for human-waste containers are all Type 1 machines.

9.3 Human-waste containers include bed pans, urine bottles, commodebowls, enema and emesis containers, and suction bottles.

9.4 WDs currently available may be divided into two groups: flusher-disinfectors in which there is no detergent wash stage – all soil removal isaccomplished by the physical action of water; and washer-disinfectors inwhich there is a wash stage after the initial flushing stage to remove grosssoiling. While the former may be less expensive, the latter design may be usedto process a wider range of items such as support frames for disposablebedpans, raised toilet seats, jugs and bowls etc.

Choice

9.5 WDs for human-waste containers are one of two available systems forproviding for the needs of bed-dependent patients. The alternative systemuses disposable containers, made of cellulose pulp, which are disposed of,complete with their contents, using a macerator. When properly installed,maintained and operated either system can provide a satisfactory solution forthe provision of human-waste containers.

9.6 Factors to be considered in making the choice include:

• the relative capital and running costs;

• the storage space required for an appropriate working stock ofdisposables;

• the peak throughput required;

• the need to provide for the cleaning and disinfection of support framesused with disposable bedpans;

• whether the flexibility to clean and decontaminate other sanitary itemsis required, and so on.

A review of these factors was published in 1991 (Rollnick) and should beconsulted for further information.

Load handling equipment

9.7 The load handling equipment may be specific for the containers to beprocessed or may be designed to accommodate a range of differentcontainers without the need to change load carriers.

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9.8 When a range of items are to be processed eg raised toilet seats, jugs,bowls, disposable bedpan support frames, as well as bedpans and urinebottles, the load carrier should be designed to accept these without the needto change carriers or add accessories. This reduces the operator time, thestorage space required and the risk of loading errors. When it is necessary tochange carriers or add accessories this should be a simple operation notrequiring the use of tools.

9.9 The loading capacities from currently available machines are either onebedpan/two urine bottles per cycle or two bedpans/four urine bottles per cycle.The higher capacity machine is the preferred option in most cases because ofits increased capability to deal with peak demands. For certain applications (egGU wards) designs capable of carrying up to eight urine bottles per cycle areavailable.

Standard specifications

9.10 WDs for human-waste containers should conform to the specificationsin BS 2745: Part 1: 1993 and BS 2745: Part 2: 1993 and the safetyspecifications in BS EN 61010: Part 1.

9.11 An EU standard is in preparation for WDs for human-waste containersand for specific safety requirements for WDs.

Additional specifications

9.12 The WD should be equipped to provide automatic emptying of human-waste containers. Manual emptying prior to, or during, the loading ofcontainers into the WD should not be required.

9.13 When a cold water rinse is used after the disinfection cycle, the waterused shall not have been stored in a tank or cistern within the WD at atemperature above 20°C or below 60°C for more than four hours.

9.14 Consideration should be given to specifying an in-built condensersystem to obviate the need for an external ventilation connection.

9.15 When required for connection to a hard water supply, a dispensingsystem should be specified to add detergent-descaler to the water duringthe washing stage of the process.

9.16 The WD should flush the residual soil from the emptied containerswith a discharge volume of no less than 15 litres to ensure adequateclearance of solids from the drainage system. The total volume of water usedper cycle may be significantly greater than this value and the volume of waterrequired per load item processed should be a consideration when choosing aWD.

Operating cycle

9.17 The WD should perform the following operational stages in each cycle:

• emptying – this should take place automatically and is usually effectedand controlled by closing the door;

Some WDs are provided with twochemical additive dispensing systemsas standard giving the option to add adetergent wash stage for processingspecific items

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• flushing – removing residual soil from the containers with water at nomore than 35°C;

• washing – removing any remaining soil by washing with water, waterand detergent, or water and detergent/descaler;

• rinsing – removing any residual detergent or detergent/descaler;

• thermal disinfection – raising the temperature of the load to the presettemperature (using hot water or steam) and maintaining thetemperature for the required disinfection holding time.

The following stages may be included if required by the user:

• cooling – rinsing the hot load with cold water to reduce thetemperature of the load;

• drying – purging the load and chamber with heated air to removeresidual moisture.

Disinfection requirements

9.18 Thermal disinfection using moist heat is the preferred method; none ofthe equipment intended to be processed in this type of WD is unable towithstand thermal disinfection within the specified temperature range andthere is no justification for the use of chemical disinfection.

9.19 The WD should be programmable to provide a thermal disinfectionprocess within the temperature range 65–90°C for disinfection times between10 minutes and one second respectively. The preferred disinfection process is80°C for one minute.

9.20 A post-disinfection cold water rinse is available on some WDs. This isintended to cool the load so that it can be handled, and/or used, immediatelyat the end of the cycle. However, the advantage in shortening the time beforethe item can be re-used is minimal and, since the final product is wet, it hasto be dried manually – eg using paper towels.

9.21 When thermal disinfection is the final stage of the cycle, the hot loadat the end of the cycle dries rapidly as the water evaporates from the surface– cooling the load at the same time.

Drying stage

9.22 Although a hot air drying stage is available on many current models,drying by evaporation after the hot disinfection/rinse stage is sufficient in mostcases.

9.23 A hot air drying stage should be specified if the WD is to be used toprocess a range of other items.

Instrumentation/recorders

9.24 The WD should be fitted with a chamber temperature indicatinginstrument to show the temperature attained during the disinfection stage.


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10.0 Washer-disinfectors for surgical instruments andassociated equipment

Introduction

10.1 This chapter discusses specifications for WDs intended to be used forcleaning and disinfecting surgical instruments and associated equipmentincluding instrument trays (eg Edinburgh trays), bowls and hollowware.

10.2 The guidance given here assumes that the WD is to be used todecontaminate medical devices and that the essential requirements of the EUDirectives discussed in Chapter 1 must be met.

10.3 WDs for this purpose may be Type 1 or Type 2 machines.

Type 1 machines

10.4 Single chamber cabinet washers for surgical instruments and associatedequipment may be either:

• simple “deluge” washers primarily intended for bowls and hollowwarebut also suitable for dealing with simple easy to clean instruments;

• designed to accept inter-changeable load carriers, typically with rotatingspray arms or other devices to ensure a uniform wash action with severallayers of load items.

The spacing between layers should be designed to accommodate a number ofwire mesh baskets full of instruments or should be more widely spaced toaccept and correctly position large bowls, instrument trays, re-usable rigidcontainers and similar items. Spacing should also allow for anaestheticaccessories to be located and processed, as well as specialist carriers withconnections for particular instruments such as rigid endoscopes and MATinstruments.

10.5 Since all stages of the cycle take place in the same chamber, it is notpossible to get physical separation between the dirty and clean stages of thecycle. Assurance that the load will not be recontaminated is dependent uponthe efficacy of the cleaning and disinfecting stages in decontaminating theinterior of the WD as well as the load.

Type 2 machines

10.6 Continuous process washers, other than those designed as automaticultrasonic cleaners only, are usually designed to accept inter-changeable loadcarriers (see above).

10.7 Compared with Type 1 machines they have a higher throughput and,for a similar process, achieve some decrease in overall cycle time.

10.8 Since the load is moved through the machine as the cleaning anddisinfection cycles proceed it is possible to get excellent physical separationbetween dirty and clean load items.

10.9 There may be some loss of operational flexibility when this type ofmachine is used for several applications at a time, eg if it is used to process

anaesthetic accessories the increased drying time, necessary for thisapplication, will slow the passage of other loads passing through the WD.

10.10 WDs of this type are large, expensive pieces of equipment and theiruse is only justified in centralised production units.


10.11 WDs for surgical instruments and associated equipment shouldconform to the specifications in BS 2745: Part 1: 1993 and BS 2745: Part 3:1993 and the safety specifications in BS EN 61010: Part 1.

10.12 An EU standard is in preparation for WDs for surgical instruments andassociated equipment and for specific safety requirements for WDs.


10.13 The automatic controller of Type 2 machines should prevent initiationof any further operating cycles if there is an inadequate supply of thechemical additives required for the next cycle.

10.14 Whenever practicable the WD should be of the double-ended passthrough type to facilitate physical segregation of dirty and decontaminateditems.

10.15 The design should permit installation through the wall between thedecontamination area and the clean area with effective sealing to preventeither passage of air from dirty to clean areas or excessive air loss from theclean area (normally maintained at a pressure above atmospheric).


10.16 A number of different types of carrier may be required toaccommodate the range of items to be processed. The range of carriersrequired in an SSD may include:

• a multi-layer carrier for instruments in wire mesh baskets (wire meshbaskets to include a number with retaining systems for smallinstruments);

• a two layer carrier for small hollowware and instrument trays;

• a single layer carrier for large bowls, Edinburgh trays etc;

• a rigid endoscope/MAT instrument carrier;

• an anaesthetic accessories carrier.

10.17 The load carriers must protect instruments from mechanical damageduring the wash process and must also orientate the instruments to facilitateproper cleaning providing, when necessary, a direct connection between thewater flow and the lumen of the load item.

10.18 The specification for load handling equipment should include theprovision of appropriate tabling to permit sorting of instruments and loadingof load carriers and, after processing, the unloading of load carriers.

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10.0 Washer-disinfectors for surgical instruments and associated equipment

10.19 When double-ended WDs are specified a conveyor will normally berequired to return load carriers from the unloading to the loading end. Wherethis passes through the wall between the packing room and decontaminationroom there should be a pass through hatch with interlocked doors.

Operating cycle

10.20 The WD should perform the following operational stages in eachcycle:

• flushing – removing gross contamination from the items in the loadwith water at a temperature not exceeding 35°C;

• washing – removing any remaining soil by washing with water, waterand detergent, or water and enzymic cleaner. Several sub-stages maybe used consecutively to provide a combination of treatments; physicalremoval of the soil may be by the impingement of water jets or byultrasonication or both consecutively;

• rinsing – removing any residual detergent or enzymic cleaner. Thisstage may be combined with the thermal disinfection stage whichfollows;

• thermal disinfection – raising the temperature of the load to thepreset temperature (using hot water or steam) and maintaining thetemperature for the required disinfection holding time;



10.21 The load, the load carriers and the internal surfaces of the WD chambershould be subjected to a thermal disinfection cycle. This should ensure that allsurfaces to be disinfected are exposed to moist heat for a period and at atemperature not less than specified in Table 2 or a process of demonstratedequivalence.

Drying stage

10.22 The drying of the load is greatly facilitated by the thermaldisinfection/hot rinse stage. In Type 1 machines with a low throughput dryingby flash evaporation from the hot load may be sufficient. Individual items forwhich drying is more critical may be transferred to a separate drying cabinet.

10.23 For more critical applications and in Type 2 machines it is normalpractice to include a hot air drying stage.

10.24 Thorough drying is of great importance. Products which are to besterilized must be thoroughly dry as should products which are to be usedwithout further treatment if there is not to be a significant risk ofrecontamination by, and growth of, micro-organisms.

The drying stage may be omitted onType 1 machines particularly for small“table-top” machines.Additional chemical treatments mayalso be included if required by theuser.The addition of “rinse-aids” may berequired to assist drying and tominimise “spotting” (deposits ofwaterborne salts) if purified water isnot used for the final rinse.The addition of instrument lubricantsduring the final rinse should beavoided whenever possible.

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10.25 The extent of necessary monitoring depends on the particularapplication. As a minimum for the thermal disinfection stage the attainmentof the required temperature should be monitored independently of the cyclecontroller, displayed on a temperature indicator or recorder, and recorded.

10.26 When the WD is to be used to decontaminate medical devices – andthe technical Standards described in the essential requirements of the EUDirectives discussed in Chapter 1 must be met – additional monitoringfacilities will be required.

10.27 The WD should be equipped with monitoring and recording devices tomonitor the critical variables which affect the outcome of the cleaning anddisinfection processes. This may include some, or all, of the following:

• pump pressure, water flow and temperature at each process stage;

• the flow or volume admitted of each chemical additive used (or, whenapplicable, by direct measurement of the concentration);

• the chemical purity of the final rinse (by measurement of electricalconductivity);

• the flow and temperature of the hot air used for drying.

Test connections

10.28 Test connections should be provided to permit the connection ofthermocouples to be used during validation and periodic testing.

10.29 When additional monitoring is provided (see above), a separate testconnection should be provided for each sensor to permit periodic verificationof the installed system by comparison with a calibrated test sensor.

Visual inspection following thedecontamination process is not ofitself sufficient to determinewhether the process wassuccessful.The decontamination process mustbe subject to validation and thenroutinely monitored to ensure thatthe process remains within thevalidated limits. Further guidanceis given in HTM 2030 ‘Operationalmanagement’ and ‘Validation andverification’.

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11.0 Washer-disinfectors for anaesthetic accessories

Introduction

11.1 This chapter discusses specifications for WDs intended for use incleaning and disinfecting anaesthetic accessories. These items are oftenintended for use without further reprocessing.


11.3 Dedicated equipment for anaesthetic equipment would usually only bejustified when there is a particularly heavy demand; most anaestheticdepartments now use single use and/or filter protected patient circuitry.

11.4 Although dedicated WDs for anaesthetic equipment are commerciallyavailable their use is declining due to the changing pattern of equipment andaccessories use in anaesthetic departments.

11.5 There is still a requirement for this type of equipment to bedecontaminated because of its use in respiratory monitoring where the use offilters may not be practicable.

11.6 Dedicated anaesthetic WDs are usually Type 1 machines but when thisfacility is provided as an option with WDs for surgical instruments they may beType 1 or Type 2 machines (see Chapter 10).


11.7 WDs for surgical instruments which can accept inter-changeableloading racks may be adapted to deal with anaesthetic accessories using aloading rack designed to hold anaesthetic breathing circuits, rebreathing bagsand self-inflating resuscitator sets, face masks etc.

11.8 The design of load carrier should ensure that each hollow or tubularitem can be connected to a spigot through which flushing, washing solutionsand the water for rinsing and thermal disinfection can be directed into thelumen of the load item.

11.9 Whenever practicable the WD should be of the double-ended passthrough type to facilitate physical segregation of dirty and decontaminateditems.

11.10 The design should permit installation through the wall between thedecontamination area and the clean area with effective sealing to preventeither passage of air from dirty to clean areas or excessive air loss from theclean area (normally maintained at a pressure above atmospheric).

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11.11 WDs for anaesthetic accessories should conform to the specifications inBS 2745: Part 1: 1993 and BS 2745: Part 3: 1993 and the safety specificationsin BS EN 61010: Part 1.


Operating cycle

11.13 The WD should perform the following operational stages in each cycle:

• flushing – removing gross contamination from the items in the loadwith water at less than 35°C;

• washing – removing any remaining soil using water and detergent orwater and enzymic cleaner. Several sub-stages may be usedconsecutively to provide a combination of treatments; physical removalof the soil should be by flushing through lumens and by theimpingement of water jets on external surfaces of load items.Ultrasonication is not effective for items made from flexible rubber orplastic;

• rinsing – removing any residual detergent. This stage may be combinedwith the thermal disinfection stage which follows;

• thermal disinfection – raising the temperature of the load to the presettemperature (using hot water or steam) and maintaining thetemperature for the required disinfection holding time;


The drying stage may be omitted if a separate drying cabinet is to beprovided. No additional chemical treatments should be necessary.


11.14 Many anaesthetic accessories will be used without furtherdecontamination treatment.

11.15 The load, the load carriers and the internal surfaces of the WDchamber should be subjected to a thermal disinfection cycle. This shouldensure that all surfaces to be disinfected are exposed to moist heat for aperiod and at a temperature not less than one of those specified in Table 2 ora process of demonstrated equivalence.

11.16 The use of chemical disinfection is particularly contra-indicated becauseof the possibility of residuals being absorbed into the polymeric materials, ofwhich the anaesthetic accessories are made, and then being evolved as irritantor toxic gases during use.

Drying stage

11.17 Thorough drying of anaesthetic tubing and other accessories isessential whether or not they are to be subjected to a furtherdecontamination process, eg sterilization.

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11.18 Because of the thermal characteristics of the materials and thestructural complexity of the items, drying with a current of warm air is arelatively slow process and may take more than twice as long as an equivalentsized load carrier filled with steel instruments. It is, for example, very difficult toremove the residual water from inside long lengths of corrugated tubing.

11.19 When anaesthetic accessories are processed through a WD for surgicalinstruments the extended hot air drying stage required will significantly reducethe throughput; if significant quantities of anaesthetic accessories are to bedecontaminated consideration may need to be given to the provision of aseparate drying cabinet.

11.20 Whether within the machine, or within drying cabinet, the flow ofwarm dry air should be directed through and over the items to be dried.


11.21 The extent of necessary monitoring depends on the particularapplication. As a minimum for the thermal disinfection stage the attainment ofthe required temperature should be monitored independently of the cyclecontroller, displayed on a temperature indicator or recorder, and recorded.

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12.0 Washer-disinfectors for endoscopes

Introduction

12.1 This chapter discusses specifications for WDs intended for cleaning anddisinfection of flexible endoscopes (fibre-optic or video) and rigid endoscopesand their accessories.


12.3 WDs for flexible fibre-optic endoscopes are all Type 1 machines; theform of the chamber is often complex and sculpted to provide appropriatesupport to the endoscope(s) being processed. WDs for rigid endoscopes maybe Type 1 or Type 2 machines.

12.4 Disinfection may be achieved:

• for most rigid endoscopes and other items which are not heat sensitive,by direct contact of the load items with moist heat at a temperature inexcess of 65°C and below 95°C. The preferred temperature is 80°C forno less than one minute;

• for fibre-optic and other heat sensitive equipment, by direct contact ofthe load items with a chemical disinfectant.

12.5 Automated WDs for endoscopes are preferred to manual cleaning,whether followed by a manual or automated disinfection procedure. This isboth for the safety of the user and also because it provides a more consistent,validated process with a higher level of assurance of attaining the requiredstandards than can be achieved with manual cleaning.


12.6 WDs for rigid endoscopes which can withstand thermal disinfectionand steam sterilization are similar to WDs for surgical instruments andassociated equipment and should conform to the specifications in BS 2745:Part 1: 1993 and BS 2745: Part 3: 1993 and the safety specifications in BS EN 61010: Part 1.


12.8 There are currently no British Standards for WDs intended for use withthermolabile endoscopes. An EU standard for WDs for thermo-labileequipment including fibre-optic endoscopes and videoscopes is in preparation.


12.9 WDs for endoscopes which employ a thermal disinfection stage shouldmeet all the requirements specified for WDs for surgical instruments (seeChapter 10).

Users should seek advice from themanufacturer of the endoscope asto the most suitable method ofdisinfection and the limiting valuesof process variables (egtemperature) for particularendoscopes.

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WDs with a chemical disinfection stage

12.10 The WD should be an enclosed system. It should be a requirement forthe lid to be locked before it is possible to start a cycle, and it should not bepossible for the operator to interrupt a cycle before completion.

12.11 The control system should permit regulation of pump pressure and inletpressure to the various connections to allow the WD to be adjusted forparticular types of instrument. It is desirable that this should be aprogrammable option on the automatic controller.

12.12 The WD should discharge solutions of cleaning agents to drain aftereach operating cycle unless the WD is equipped with means to verify theconcentration of the chemical additive which remains active in the solution.(For some cleaning agents this may be achieved by continuous monitoring ofin-use concentration using an appropriate ion selective electrode (ISE).)

12.13 The disinfectant solution should be used once and discarded.Alternatively, when systems which re-use disinfectant solutions for a numberof cycles are employed, means should be incorporated to ensure that theautomatic cycle will not start when the disinfectant concentration has fallento, or below, the minimum recommended by the manufacturer orestablished by independent testing – eg for a 2% solution of glutaraldehydea limiting concentration of 1.5% would be recommended (Babb et al 1992).

12.14 The rinsing stage should be carried out with water of a quality thatdoes not lead to recontamination of the endoscope with micro-organismscoming from the incoming water supply reservoirs, including pipeworkwithin the machine.

12.15 The rinse water from one process should not be retained and used insubsequent cycles but should be discharged to drain.

12.16 There should be no static water stored within the WD at atemperature above 10°C or below 55°C for more than four hours if it isintended to come into contact with the load. This should be controlled andmonitored by the automatic controller of the WD.

12.17 WDs should be designed and constructed such that they are able to bedrained and dried when not in use.

12.18 The available operating cycles on the automatic control system shouldprovide for a WD decontamination cycle to ensure that all pipework, tanks,pumps, water filtration systems and other fittings which are used to carryaqueous solutions intended to come into direct contact with the product arecleaned and disinfected. The decontamination cycle shall be user selectable.

12.19 The automatic controller should control the temperature of thedisinfectant solution or monitor the temperature to ensure that it is above avalue previously determined during validation studies (see HTM 2030‘Validation and verification’ for more information).

12.20 The WD should be equipped with a recorder or data logger to recordthe attainment of the specified value of critical cycle variables throughout thecycle.

Re-use of the same disinfectantsolutions for several operating cyclesis often justified on grounds ofeconomy. This may be a falseeconomy if second and subsequentprocesses with the same batch ofdisinfectant solution are not subject tothe same control as the initial use

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12.21 The WD should be equipped with means to contain or vent fumes andgases from the disinfectant solution to ensure that operators are not exposedto hazardous concentrations of the chemicals used. The WD should beprovided with means to vent fumes from the chamber before allowing accessto the operator.


12.22 The loading system should be appropriate to the range of endoscopeswhich it is intended to process.

12.23 Some endoscopes are not designed to be completely immersed inliquid and the operating head must remain above the liquid level.

12.24 The load carrier needs to provide connection to the various channelswithin the endoscope to allow the cleaning and disinfection solutions to flowthrough the channels and may need to provide holders for disassembledcomponents, valves etc.

Compatibility with items to be processed

12.25 Attention is drawn to the need to ensure that for any particular loaditem that all cleaning and decontamination processes are carried out in strictaccordance with the manufacturer’s instructions. All endoscopes, butparticularly those incorporating fibre-optic systems, are easily damaged.

12.26 If the process conditions recommended by the manufacturer, includingmaximum temperatures, internal pressures, nature of any physical treatmentsuch as ultrasonication, and limitations on the chemical additives which maybe used, are ignored serious damage can be caused to these expensiveinstruments.


12.27 The standard of disinfection required should be defined by the user inconsultation with the control of infection officer.

12.28 In general:

• endoscopes which, in use, are passed into sterile body cavities areconsidered to be invasive and must be sterilized;

• endoscopes which, in use, come into contact with mucous membranesbut do not invade sterile body cavities are non-invasive and can bedecontaminated using high-level disinfection.

Endoscopes of this type are beingphased out of service.

Some endoscopes requireprotective caps to be fitted tosensitive components before theycan be decontaminated in anautomated WD, eg videoscopesneed a protective cap on the videoplug

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12.29 The choice of disinfectant should be based on the rigours of thedisinfection procedure required, and on the compatibility with theendoscope and WD and the constructional materials of both.

Rinse water: quality requirements

12.30 For invasive endoscopes the final rinse water should be sterile and fornon-invasive endoscopes it is preferable that it is sterile.

12.31 The most reliable method of providing water of the quality requiredfor the final rinse is to use sterile “bottled” water.

12.32 Alternatively it is possible to produce water of appropriate quality bytreatment of the local piped water supply. This may be provided adjacent to,or within, the WD.

12.33 The nature and extent of treatment will depend in part on the qualityof the local water supply but normally should include at least the followingsteps:

• pre-filtration to remove suspended particulate matter (this may requireone or two filtration stages but the final stage should be with a filterthat will retain particles of 5 µm or larger);

• filtration through a bacteria retentive filter (0.22 µm).

The operating system should include:

• means to monitor the integrity of the filter or warn of failure;

• means to disinfect or sterilize the filter and the downstream waterdistribution system between uses or at four hourly intervals. Thisshould preferably be by exposure to moist heat but a chemicaldisinfection process may also be used. A demountable system whichallows the filter and downstream distribution system to be removed,dried and steam sterilized between sessions provides an acceptablealternative;

• means to maintain the filter with a constant flow of water (not leftwet in static water);

• means to inhibit microbial growth in water in the storage anddistribution system downstream of the filter. This may be achieved byrecirculation through an appropriate UV light disinfection system or bymaintaining the water at elevated temperature eg > 80°C.

12.34 The design of the pipework, tanks, valves and pumps to avoid deadlegs and areas where microbial growth may proliferate is critical to themaintenance of the system from microbial contamination. All fittings and pipeconnections should be pharmaceutical grade sanitary fittings.

Operating cycle requirements

12.35 The following operating cycle presents a general specification whichmay need to be adapted for particular instruments. It assumes thatimmediately after use, and before transfer to decontamination, the insertiontube will have been wiped clean and that all channels will have been flushedthrough to remove gross contamination and ensure that they are free fromblockages.

If heated storage is used it will benecessary to cool the watersupplied to the WD to ensure thatthe endoscope(s) are not damagedby exposure to too high atemperature

There is a potential for electrolyticaction between different materialseven when one material is part ofthe load and the other is part ofthe WD. This may result incorrosion of the load items and/orthe WD.Guidance on suitable disinfectantsand exposure times are given inHTM 2030 ‘Validation andverification’ and in the MDABulletin on ‘Decontamination ofendoscopes and their accessories’

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12.36 It is also assumed that any manual dismantling required (includingremoval of single use items, separation of accessories, removal of valves andcovers, and disassembly) has taken place before the instruments are placedinto the WD.

12.37 The operating cycle should include:

a. a leak test to verify that the endoscope is undamaged and will notsuffer irreparable damage during exposure to the cleaning anddisinfection process. (This should be a user selectable option);

b. flushing with water at a temperature not exceeding 35°C (thismaximum temperature is necessary to minimise the coagulation ofprotein and consequent fixing of the soiling);

c. a flow test to ensure that all channels which should be irrigated withcleaning solution and disinfectant solutions are not blocked;

d. washing with an aqueous solution of detergent or an enzymic cleaner;when detergent solutions are used this may be at elevated temperaturebut should not exceed 60°C (see paragraphs 12.25 and 12.26).

The efficacy of chemical cleaning agents (detergents and enzymiccleaners) is affected by concentration, temperature, contact time andthe presence or absence of materials/chemicals which will react with,and therefore inactivate, the chemical cleaning agent. The WD shouldprovide means to control all these factors to the extent necessary toobtain satisfactory and reproducible cleaning.

For most rigid endoscopes ultrasonication may be used except for thetelescope; ultrasonication generally is not suitable for use with opticalor fibre-optic systems.

The pressure at which fluids are pumped through the internal channelsof the endoscope should be controlled and maintained within the limitsspecified by the endoscope manufacturer;

e. rinsing to remove chemical additives used during the cleaning process;

f. drying to remove excess water before transferring to the disinfectionstage where residual water can cause serious dilution of thedisinfectant. This stage may be optional unless the load has to bemanually transferred to an automatic disinfector;

g. disinfection. For rigid endoscopes thermal disinfection may bepracticable (see endoscope manufacturer’s instructions) and if so shouldbe used. For fibre-optic endoscopes there is usually an uppertemperature limit of 60°C for processing conditions; thermaldisinfection is impracticable and chemical disinfection should be used.

The efficacy of chemical disinfectants is affected by concentration,temperature, contact time and the presence or absence ofmaterials/chemicals which will react with, and therefore inactivate, thedisinfectant. The WD should provide means to control all these factorsto the extent necessary to obtain satisfactory and reproducibledisinfection;

h. rinsing to remove disinfectant. After an effective cleaning anddisinfection process the microbial quality of the final rinse water willdetermine the microbial contamination which may be present on theendoscope;

j. drying.

Although this should have beenverified before the instrument wasplaced in the WD, blockage canoccur during processing whensoiling dislodged from one placebecomes trapped in a morerestricted part of the instrument

The rinse stage between cleaningand disinfection may be omitted ifthe disinfectant and cleaningagents are known to becompatible and the disinfectantpreparation is used only for asingle cycle.

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Drying stage

12.38 Drying may be achieved by purging with heated dry air; means shouldbe provided to ensure that the temperature of the endoscope is not raisedabove the maximum specified by the endoscope manufacturer. The quality ofair used should not contribute to physical, chemical or microbialrecontamination of the decontaminated item.

12.39 Drying may also be accomplished by purging the decontaminateditem with 70% alcohol and allowing this to evaporate. The quality of thealcohol used should not contribute to physical, chemical or microbialrecontamination of the decontaminated item. In particular spore-free alcoholshould be used.

Decontamination of the washer-disinfector

12.40 Automatic WDs for endoscopes may themselves act as a source ofcontamination for the decontaminated items.

12.41 The design, installation and operation of the WD, including the qualityof connected services, may contribute to the problem.

12.42 The WD should include a flushing stage for the WD pipework aftereach cleaning cycle to remove dislodged debris, biofilm etc so that thesecannot initiate a contamination problem.

12.43 All tanks used for the storage of water or aqueous solutions shouldbe designed and constructed to ensure that they are free draining andcleanable.

12.44 The use of soft water can help alleviate this problem but it should benoted that base exchange softeners, and also de-ionisers, may themselves bea source of microbial contamination and can lead to high microbial countsof water borne organisms. These organisms are typically of species adaptedto develop biofilms and the extracellular layers present in these biofilmsprovide good protection against microbicides.

12.45 Microbial colonisation of pipework may occur if the system is notdisinfected regularly or if there is inappropriate cleaning and maintenance ofthe machine.

12.46 The WD manufacturer should provide information on cleaning anddisinfection procedures and compatible chemicals for these purposes.

Requirements for control of the disinfection stage

12.47 The chemical disinfection system must:

• ensure that the disinfectant solution temperature is either controlledat a pre-set temperature or is above a specified minimum temperatureon which the exposure time was based;

• ensure that all parts of load items to be disinfected are in contact withthe disinfectant. This should include means to ensure the eliminationof air bubbles etc;

Some disinfectant formulationshave an upper temperature limitbeyond which the disinfectant orits adjuvants in the formulation aredecomposed or inactive

The use of hard water, water ofinadequate microbiological qualityor water stored in tanks atambient temperatures forprolonged periods will promotecontamination and the formationof biofilms within the machine

Most endoscope manufacturersadvise that the lens system shouldnot be exposed to alcohol forprolonged periods, althoughnormally two to five minutesexposure will cause no damage

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• avoid the risk of recontamination with micro-organisms from the WD,other load items or the connected services.


12.48 The extent of necessary monitoring depends on the particularapplication. As a minimum for the thermal disinfection stage the attainmentof the required temperature should be monitored independently of the cyclecontroller, displayed on a temperature indicator or recorder, and recorded.

12.49 When the WD is to be used to decontaminate medical devices and thetechnical Standards described in the essential requirements of the EUDirectives discussed in Chapter 1 must be met additional monitoring facilitieswill be required.

12.50 The WD should be equipped with monitoring and recording devices tomonitor the pump pressure (or water flow) and temperature at each processstage, the flow or volume admitted of each chemical additive used (or, whenapplicable, by direct measurement of the concentration), the chemical purityof the final rinse (by measurement of electrical conductivity), and the flow andtemperature of the hot air used for drying.

Test connections


12.52 When additional monitoring is provided (see above) a separate testconnection should be provided for each sensor to permit periodic verificationof calibration of the installed system by comparison with a calibrated testsensor.

Visual inspection following thedecontamination process is not ofitself sufficient to determinewhether the process wassuccessful. The decontaminationprocess must be subject tovalidation and then routinelymonitored to ensure that theprocess remains within thevalidated limits. Further guidanceis given in HTM 2030 ‘Operationalmanagement’ and ‘Validation andverification’

Recontamination could lead totransfer of infection or inaccuratediagnosis if the contaminant iserroneously assumed to havecome from the patient

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13.0 Laboratory washer-disinfectors

Introduction

13.1 This chapter discusses specifications for laboratory WDs.

13.2 Laboratory WDs may be used to process components or equipment foruse in the manufacture of medical devices or medicinal products or they maybe used to process apparatus and equipment for use in clinical, or other,laboratories.

13.3 When used to process components or equipment for use in themanufacture of medical devices or medicinal products the design, construction,validation, operation and maintenance of these WDs will need to meet therequirements of the relevant EU Directives for medical devices or medicinalproducts (see Chapter 1).

13.4 WDs for both these applications may be machines of Type 1 or Type 2.

13.5 Commercially available machines offer a similar range of options tothose WDs intended for the decontamination of surgical instruments andassociated equipment (see Chapter 10).


13.6 The load handling equipment must be specific for the load items to beprocessed to ensure both that the load items are retained in the load carrierand that the external and any internal surfaces of the load items are reachedeffectively by the cleaning and disinfecting liquids throughout the cycle.


13.7 There are no standard performance specifications specifically forlaboratory WDs. For most applications the WD should conform to the relevantparts of the specifications in BS 2745: Part 1: 1993 and BS 2745: Part 3: 1993which includes, for example, specific requirements for WDs used for thedecontamination of glassware.

13.8 Laboratory WDs should conform to the safety specifications given in BS EN 61010: Part 1.

Operating cycle

13.9 The WD should perform the following stages in each cycle:

• flushing – removing gross contamination from the items in the load withwater at a temperature not exceeding 35°C;

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• washing – removing any remaining soil by washing with water, waterand detergent, or water and enzymic cleaner. Several sub-stages maybe used consecutively to provide a combination of treatments; physicalremoval of the soil may be by the impingement of water jets or byultrasonication or both consecutively;

• rinsing – removing any residual detergent or enzymic cleaner. This stagemay be combined with the thermal disinfection stage which followsand normally requires the use of purified (DI, RO or distilled) water;

• thermal disinfection – raising the temperature of the load to the presettemperature (using hot water or steam) and maintaining thetemperature for the required disinfection holding time;


For many applications in laboratories the drying stage may be omitted.

Choice of detergent/cleaning agent

13.10 The cleaning agent(s) to be used should be chosen to be appropriateto the materials of the load items, the soiling to be removed, the intendedend use of the load items and compatible with the WD. In many cases thereare highly specific requirements and a specific formulation is required.

13.11 The use of detergent and other chemical additives may not beappropriate in all cases. For example in the preparation of single-use glasscontainers for pharmaceutical applications the process is required to removedust and similar debris which have contaminated the containers duringdistribution and storage, rather than strongly adherent soiling, and vigorouswashing with water alone may be sufficient. Furthermore, if detergentsand/or other chemical additives are to be used the process must be designedand operated to ensure that the concentration of residual detergent isreduced to a level where it will not have an adverse effect on the product.


13.12 Disinfection is achieved by direct contact of the load items with moistheat at a temperature in excess of 65°C and below 95°C (see Table 2). Thepreferred temperature is 80°C for not less than one minute.

Drying stage

13.13 Drying is greatly facilitated by the final hot rinse. In general laboratoryapplications drying by flash evaporation from the hot load may be sufficientwith individual items for which drying is more critical being transferred to aseparate drying cabinet. For more critical applications, eg containers forparenteral products where residual moisture may permit recontamination andunacceptable microbial growth, drying is important. Drying is also importantfor those products which are to be sterilized subsequently since this willrequire that the item is thoroughly dry.

Laboratory WDs incorporating asolvent wash stage are alsoavailable but are beyond the scopeof this HTM

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13.14 The extent of necessary monitoring depends on the particularapplication. As a minimum when thermal disinfection is required theattainment of the required temperature should be monitored independently ofthe cycle controller and displayed on a temperature indicator or recorder.

13.15 For critical applications, eg the preparation of pharmaceuticalcontainers for parenteral products, all key variables of the process should beindependently monitored. The WD should be equipped with monitoring andrecording devices to monitor the pump pressure, water flow andtemperature at each process stage, the flow or volume admitted of eachchemical additive used (or, when applicable, by direct measurement of theconcentration), the chemical purity of the final rinse (by measurement ofelectrical conductivity), and the flow and temperature of the hot air used fordrying.

Test connections


13.17 When additional monitoring is provided (see above) a separate testconnection should be provided for each sensor to permit periodic verificationof calibration of the installed system by comparison with a calibrated testsensor.

Visual inspection following thedecontamination process is not ofitself sufficient to determinewhether the process wassuccessful. The decontaminationprocess must be subject tovalidation and then routinelymonitored to ensure that theprocess remains within thevalidated limits. Further guidanceis given in HTM 2030 ‘Operationalmanagement’ and ‘Validation andverification’

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14.0 Ultrasonic cleaners

Introduction

14.1 This chapter discusses specifications for ultrasonic cleaners.


14.3 Ultrasonic cleaners may be Type 1 or Type 2 machines.

14.4 Ultrasonic cleaners work by exposing the items to be cleaned to highfrequency sound waves in the liquid cleaning medium.

14.5 The high frequency sound waves are generated within the liquid bythe vibration of one or more surfaces of the bath; the surface(s) of the bathbeing caused to vibrate by one or more transducers bonded to the outersurface(s). The transducers convert electrical power into vibrations of therequired frequency and amplitude.

14.6 The highly effective cleaning action occurs as a result of thepenetrative agitation caused by cavitation; the rapid formation and collapse oftiny bubbles within the liquid which are generated by the high frequencysound waves.

Applications

14.7 Ultrasonic cleaners are used in a wide range of industries includingengineering, jewellery etc.

14.8 Ultrasonic treatment is particularly suitable for cleaning instruments ofhigh grade steel. Delicate instruments such as micro-surgery instruments anddental instruments can be effectively cleaned with little risk of damage.

14.9 Ultrasonic treatment is also particularly effective for cleaninginstruments that have deep interstices that may be contaminated with bodytissues, eg reamers, drills and burrs.

14.10 When combined with appropriate connection to an irrigation orflushing system ultrasonicators are also effective for cleaning cannulatedinstruments.

14.11 Ultrasonic cleaners are less effective when used to clean plastic andsimilar readily compressible materials since they absorb much of the ultrasonicenergy.


14.12 Ultrasonic cleaners, whether designed as stand alone units orincorporated into continuous process machines, should comply with the

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requirements of BS 2745: Part 3: 1993 and the safety specifications in BS EN 61010: Part 1.


14.13 The ultrasonic cleaner should be fitted with means to drain the tankwith the cleaner in situ. The tank should be free draining so that no pools ofwater are left in the tank after draining.

14.14 The tank should be heated electrically and the heaters should bethermostatically controlled.

14.15 The ultrasonic cleaner should be fitted with a timer to control theduration of exposure.

14.16 The ultrasonic cleaner should have a lid; the lid should be interlockedwith the operating system to prevent normal operation if the lid is open andshould fit securely to prevent the emission of aerosols when the cleaner is inoperation.

14.17 The ultrasonic cleaner should be effectively insulated to prevent highfrequency sound transmission at a power which could cause a healthhazard. (Note: High frequency sound is suspected of causing damage tohearing). The casing and lid should provide adequate sound proofing so thatharmonic frequencies within the audible range are not obtrusive.

14.18 The manufacturer should specify the chemical additives (detergentsand/or enzymic cleaners) which are required and which are compatible withthe process.

14.19 The manufacturer should specify the means by which the cleanermay be disinfected. This may be by the provision of a high-temperature, eg80°C cycle option, or by means of a suitable disinfectant solution. In theabsence of guidance the microbiologist should be asked to advise on asuitable procedure.

14.20 The manufacturer should specify the de-gassing time(s) which shouldbe used on start-up and, when necessary, between each load of instrumentsprocessed.

Wash cycle

14.21 The ultrasonic frequency used is typically within the range 35 ± 5 kHzand the energy input used may range from 5.0 to 20.0 Watts/litre.

14.22 Ultrasonic cleaners may be designed to operate at a single frequency,across a frequency range, or with a feedback control system claimed to adjustthe frequency in response to the loading conditions.

14.23 For medical applications aqueous solutions are used. Althoughultrasonic cleaners containing aqueous solutions may be effective attemperatures up to 90°C it is normal practice to operate those for medicalapplications at temperatures between ambient and 40°C. This minimises therate of coagulation of proteinaceous material in the soiling and is compatiblewith the use of enzymatic cleaners, many of which are rapidly destroyed athigher temperatures.

Low foaming detergents arerequired; liquid detergents usedfor washing dishes (“washing-upliquid”) are generally not suitable.Although an ultrasonicator willwork without detergent/cleanerthe cleaning action is much lesseffective

The lid interlock should ensurethat no part of the operator’sbody can be immersed in theultrasonic cleaner duringoperation; long term directexposure to ultrasound issuspected of causing arthriticconditions

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Type 1 ultrasonicators


14.24 A mechanical lifting device should be specified when the ultrasonicatoris intended to process heavy sets of instruments.

14.25 The load container, usually a wire mesh basket, should be ofappropriate size for the longest instrument to be processed.

14.26 When it is intended to process micro-surgical instruments orinstruments with fine points the load handling equipment should providemeans of retaining these in position so that the points are not blunted by theimpacts resulting from fine mechanical shaking.

Type 2 (continuous process) ultrasonicators

14.27 Continuous process WDs may incorporate an ultrasonic cleaning stagewithin the cycle programme.

14.28 Ultrasonic cleaners are also available in continuous process format witha thermal disinfection stage and with the option to provide a hot air dryingstage.

14.29 Ultrasonic cleaners with a solvent drying stage are no longercommercially available since the solvents used were CFCs which are nowprohibited under the Montreal Protocol.


14.30 If complex tabling or conveyors are required these should be specified,and preferably illustrated with a sketch plan, when seeking tenders.

14.31 When it is intended to process micro-surgical instruments orinstruments with fine points the load handling equipment should providemeans of retaining these in position so that the points are not blunted by theimpacts resulting from fine mechanical shaking.


14.32 The ultrasonic cleaner should be fitted with a temperature indicator;provision should be made for a recorder to be fitted if requested by thepurchaser.

14.33 The ultrasonic cleaner should be fitted with an indicator to show thepower consumption (in Watts), or electrical demand (in Amps) of theultrasonic transducers; provision should be made for a recorder to be fitted ifrequested by the purchaser.

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Appendix I: Glossary of terms

Automatic controller: Device that, in response to pre-determined cyclevariables, operates the WD sequentially through the required stages of thecycle(s)/process.

Biological indicator: See EN 866-1:1997.

Calibration: The set of operations that establish, under specified conditions,the relationship between values of a quantity indicated by a measuringinstrument or measuring system, or values represented by a material measureor a reference material, and the corresponding values realised by Standards.

Calorifier: A closed vessel in which water is indirectly heated under a pressuregreater than atmospheric.

Chamber: That part of the WD in which the load is processed.

Chemical disinfection: Disinfection achieved by the action of one or morechemicals; the primary purpose of which is to be microbicidal.

Continuous process machine: A machine which automatically transports theload through each stage of the operating cycle.

Chemical additive: A formulation of chemical compounds intended for usein a WD.

Cycle complete: Indication that the washing and disinfection cycle has beensatisfactorily completed and that the disinfected load is ready for removalfrom the chamber.

Cycle variables: The physical and chemical properties (eg times, temperatures,disinfectant concentration, pressures and flows) that influence the efficacy ofthe washing and processes.

Decontamination: The combination of processes, including cleaning anddisinfection and/or sterilization, used to render a re-usable item safe for furtheruse.

Disinfection: the reduction of the number of viable micro-organisms on aproduct to a level previously specified as appropriate for its intended furtherhandling or use.

Disinfection temperature: The minimum temperature of the disinfectiontemperature band.

Disinfection temperature band: The range of temperatures, expressed asthe disinfection temperature and the maximum allowable temperature whichmay prevail throughout the load during the disinfection time.

Disinfection time: The time period at which the cycle variable (egtemperature of the load, disinfectant concentration in the chamber) ismaintained at or above the value specified for disinfection.

This includes detergents,surfactants, rinse aids,disinfectants, and enzymaticcleaners

The chamber does not includesteam generators, pipework andfittings from which it can beisolated

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Door: Device provided as a means of closing and sealing the chamber.

Double-ended washer-disinfector: A WD incorporating separate doors forloading and unloading.

Fail safe: Attribute of WD design, component or its associated services thatminimises a possible safety hazard.

Fault: Recognition by the automatic controller that the pre-set cycle variablesfor the WD cycle have not been attained.

Holding time: the time period for which the cycle variables are maintained ator above the value specified for disinfection.

Hysteresis: The lagging of effect behind cause.

Inoculated carrier: See EN 866-1.

Installation test: Series of checks and tests performed after installation ofthe WD in the place of use.

Load: A collective term used to describe all the goods equipment andmaterials that are put into a WD at any one time for the purpose ofprocessing it by an operating cycle.

Loading door: Door in a double-ended WD through which the load is putinto the WD prior to processing.

Loading height: The minimum height to which the underside of the load orload container has to be raised for it to enter the loading door.

Medical device: See EN 46001: 1997.

Monitoring: The measurement of physical variables, such as the function ofthe automatic controller to check the attainment, or otherwise, of the pre-setcycle variables essential to the efficacy of the operating cycle.

Operating cycle: The complete set of stages of the process that is carried outin the sequence as regulated by the automatic controller.

Operating pressure: The gauge pressure at which the vessel is operatedduring normal use.

Override: The system by which the operating cycle can be interrupted ormodified as necessary.

Safety hazard: Potential detrimental effect on persons arising from the load.

Steam generator: Vessel designed to contain water and a heating system (ega steam coil or a fully immersed electric element) which is used to heat waterto its vapour state.

Sterile: See EN 556

Sterilization: Process used to render a product sterile (35).

Tank: A process vessel, integral to the WD, designed to hold solutions duringprocessing.

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Test organism: See EN 866-1: 1997

Test soil: Substance used to test the washing efficacy of a WD.

Thermal disinfection: Disinfection achieved by the action of moist or dryheat.

Type test: Series of tests to establish the working data for a WD type.

Unloading door: Door in a double ended WD through which the load isremoved after an operating cycle.

Usable space: Space inside the chamber which is not restricted by fixed partsand which is consequently available to accept the load.

Validation: See EN 554.

Viable micro-organism: Micro-organisms, including viruses, which arecapable of multiplication under specified culture conditions.

Warning pipe: Overflow pipe so fitted that its outlet, whether inside oroutside the building, is in a conspicuous position, where the discharge ofwater can be readily seen.

Washer-disinfector (WD): Machine intended to clean and disinfect medicaldevices and other articles used in the context of medical, dental,pharmaceutical and veterinary practice.

Waste outlet: The point from which the chamber discharges the wastefluids.

Works test: Series of tests performed at the manufacturer’s works todemonstrate compliance of each WD with its specification.

This type of machine does notinclude those designed specificallyto wash linen or clothing

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Appendix II: Abbreviations

A Amperes

AC Alternating Current

AP(S) Authorised Person (Sterilizers)

BS British Standard

°C degrees Celsius

COSHH Control of Substances Hazardous to Health

DC Direct Current

DI De-Ionised (referring to water)

EMC Electro-Magnetic Compatibility

EN European Standard

EP European Pharmacopoeia

EU Endotoxin Unit

GGMP ‘Guide to Good Manufacturing Practice for Medicinal Products’(GGMP) published in Volume IV of ‘The Rules Governing MedicinalProducts in the European Community’

HBN Health Building Note

HSE Health and Safety Executive

HTM Health Technical Memorandum

ISE Ion Selective Electrode

K Kelvin

kg kilogram

kHz kiloHertz

kVA kilo Volt Amperes

kW kiloWatt

MCA Medicines Control Agency

MDA Medical Devices Agency

mbar millibar

mg milligram

ml millilitre

m metre

MP(S) Maintenance Person (Sterilizers)

N Newtons

OEL Occupational Exposure Limit

Pa Pascal

PES Programmable Electronic System

pH The inverse of the logarithm to base 10 of the hydrogen ion activityof a solution (Solutions with pH values less than seven are acidic andthose with pH values greater than seven are alkaline)

ppm parts per million

RO Reverse Osmosis – a method of water treatment

SSM Standard Sterilization Modules (600mm x 300mm x 300mm)

SSD Sterile Services Department

TP(S) Test Person (Sterilizers)

WD Washer-Disinfector

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Appendix III: Useful addresses

UK health agencies

NHS Estates, 1 Trevelyan Square, Boar Lane, Leeds LS1 6AE Tel 0113 254 7000

Medical Devices Agency (MDA)Hannibal House, Elephant and Castle, London, SE1 6TQTel 0171 972 8000

Medicines Control Agency (MCA)Market Towers, 1 Nine Elms Lane, London SW8 5NQ Tel 0171 273 3000

NHS in Scotland Management Executive, St Andrews House, Edinburgh EH1 3DG Tel 0131 556 8400

NHS in ScotlandHealthcare Engineering and Environment Unit, University of Strathclyde,Graham Hills Building, 50 George Street Glasgow G1 1QETel 0141 548 3446

Welsh Office, Cathays Park, Cardiff CF1 3NQTel 01222 825111

Estate and Property Division, Estate Services Directorate, HPSS ManagementExecutive, Stoney Road, Dundonald, Belfast BT16 0USTel 0232 520025

Health and Safety

Health and Safety Executive, Broad Lane, Sheffield S3 7HQ. Tel. 0114-289 2345Note. Addresses of HSE area offices may be found in the local telephonedirectory

Standards organisations

British Standards InstitutionBritish Standards House, 389 Chiswick High Road, London W4 4ALTel 0181 996 9000

European Committee for Standardisationrue de Stassart 36, B-1050 Brussels

Other organisations

Institute of Healthcare Engineering and Estates Management.2 Abingdon House, Cumberland Business Centre,Northumberland Road, Portsmouth PO5 1DS. Tel. 01705 823186

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Appendix IV: Information to be supplied by themanufacturer

A4.1 The following information should be supplied by the manufacturer ofthe WD at or before the time the WD is delivered.

Standards

A4.2 Statements of, and documentary evidence to substantiate, compliancewith relevant British and EU Standards.

Instruction manual

A4.3 The manual should contain complete instructions including:

• simplified operating instructions in a durable form suitable for fixingnext to the WD;

• guidance on the types of load that may be processed in the WD andthe recommended loading patterns/load carriers to be used;

• operational limits including the maximum working temperature whichmay be attained within the WD chamber or chambers, and themaximum pressure that may be applied to the lumen of cannulatedinstruments.

A4.4 When the WD incorporates a pressure vessel (eg an integral steamgenerator) the operational limits of the pressure vessel including designpressure, maximum permissible working pressure and maximum permissibleworking temperature in accordance with the pressure systems Regulations. Avalid test certificate should be provided by the manufacturer for all pressurevessels supplied.

Instruments and controls

A4.5 The manual should include a description of each instrument andcontrol fitted to the WD including:

• the scale ranges of each and the limits of accuracy;

• evidence that the calibration of each instrument has been verified andthat the instrument is reading correctly within its limits of accuracy.

Operating cycles

A4.6 The manual should give a description of each operating cycle availableon the sterilizer.

95

Services

A4.7 The manual should give a description of all the engineering servicesrequired by the WD, specifying:

• values of the fluctuating demands placed on each service during thecourse of a normal operating cycle;

• the maximum and minimum safe supply pressures, temperatures andvoltages.

This should also include specification of the minimum acceptable water qualityfor each stage in the process (defined as pH, total dissolved solids, redoxpotential, electrical conductivity).

Safety

A4.8 Safety information should include:

• description of any safety hazard that may arise in the normal operationof the WD and recommended precautions to avoid them;

• description of all safety devices including their recommended settingsand any means provided to override and reset them;

• description of the chemical additives with which the WD is intended tobe used.

Machine characteristics

A4.9 The manual should include a description of the machine, specifying thetotal volume of the chamber: This should include the following information:

• dimensions of the usable space and its capacity expressed either as anintegral number of load baskets based on the standard sterilizationmodule (SSM) or as a specific number of identified load items eg thenumber of bed pans;

• parts of the usable chamber space which are fastest and slowest toattain the disinfection temperature, and those parts which are hottestand coolest during the disinfection holding time.

Maintenance manual

A4.10 Two copies should be provided. The manual should include:

• a planned preventive maintenance programme, consistent with theprinciples outlined in HTM 2030 ‘Operational management’, togetherwith detailed instructions for the procedures contained within it;

• a list of any special tools and equipment required for periodicmaintenance and testing;

• diagrams of all electrical, steam, compressed air, water, chemicaladditive dosing systems, and ventilation and drainage connections.

• a complete list of all spare parts, indicating all parts which should beheld in stock and that may require replacement during the normalworking life of the WD together with their usage rates;

96

Appendix IV: Information to be supplied by the manufacturer

• guidance on tracing and correcting likely causes of malfunction;

• method of adjusting and calibrating the pressure, temperature and flowrate indicating or recording systems.

97

Appendix IV: Information to be supplied by the manufacturer

References

Acts and Regulations

SI 201: 1995 Public supply contracts regulations. TSO, 1995.

SI 2169: 1989 Pressure systems and transportable gas containersregulations. TSO, 1989.

SR 471: 1991 Pressure systems and transportable gas containersregulations (Northern Ireland). TSO, 1991.

SI 2372: 1992 Electromagnetic compatibility regulations. TSO, 1992.

SI 2793: 1992 Manual handling operations regulations. TSO, 1992.

SI 2932: 1992 Provision and use of work equipment regulations. TSO,1992.

SI 2966: 1992 Personal protective equipment at work regulations. TSO,1992.

SI 3004: 1992 Workplace (health, safety and welfare) regulations. TSO,1992.

SI 3246: 1994 The control of substances hazardous to health (COSHH)regulations. TSO, 1994.

Public Health Act 1961. TSO.

Medicines Act 1968. TSO.

The Model Water Bye-laws 1986. TSO.

European Union (EC) Directives

Council Directive laying down the principles and guidelines of goodmanufacturing practice for medicinal products for human use(91/356/EEC). Official Journal of European Communities, L193, 17.7.91, p.30.

Council Directive concerning medical devices (93/42/EEC). Official Journalof European Communities, L169, 12.7.93, p.1.

NHS Estates publications

Concode: Contracts and submissions for the NHS Estate – Contractprocedures. NHS Estates, TSO, 1994.

Model Engineering Specifications. NHS Estates, TSO, 1993 (amended1995)(issued in 4 volumes).

98

Health Building Notes (HBNs)

13. Sterile services department. NHS Estates, TSO, 1992.Sup 1 Ethylene oxide sterilization services. NHS Estates, TSO,1994.

15. Accommodation for pathology services. NHS Estates, TSO, 1991.

26. Operating department. NHS Estates, TSO, 1991.(out of print).

Health Technical Memoranda (HTMs)

2007. Electrical services supply and distribution. NHS Estates, TSO, 1993.(issued in four parts).

2010. Sterilization. NHS Estates, TSO, 1994/97. (issued in six parts).

2011. Emergency electrical services. NHS Estates, TSO, 1995. (issued infour parts).

2020. Electrical safety code for low voltage systems (Escode-LV). NHSEstates, TSO, 1994. (issued in two parts).

2022. Medical gas pipeline systems. NHS Estates, TSO, 1994. (issued infive parts)

Sup 1 Dental compressed air and vacuum systems. NHS Estates,TSO, 1996.Sup 2 Piped medical gases in ambulance vehicles. NHS Estates,TSO, 1997.

2025. Ventilation in healthcare premises. NHS Estates, TSO, 1994. (issuedin four parts).

2027. Hot and cold water supply, storage and mains services. NHSEstates, TSO, 1995. (issued in four parts).

2031. Steam supply for sterilization. NHS Estates, TSO, in preparation.

2040. The control of legionellae in healthcare premises – a code ofpractice. NHS Estates, TSO, 1993. (issued in five parts).

Firecode

83. Fire safety in healthcare premises: general fire precautions. NHSEstates, TSO, 1994.

Scottish publications

Scottish Hospital Planning Notes (SHPNs)

13. Sterile services department. Scottish Office, TSO, 1994.

15. Accommodation for pathology services. Scottish Office, TSO, 1994.

99

References

Firecode

Firecode in Scotland: policy and principles. Scottish Office, TSO, 1994.

Fire safety new health buildings in Scotland. Scottish Office, TSO, 1988.

Department of Health publications

Sterilization, disinfection and cleaning of medical equipment, guidanceon decontamination from the Microbiology Advisory Committee to theDepartment of Health Medical Devices Directorate. MicrobiologyAdvisory Committee, Department of Health, 1993.

Microbiological safety cabinets: recommendations concerning theirchoice, installation routine maintenance and use (Health EquipmentInformation No. 86). Medical Devices Agency, Department of Health, 1980.

Endoscope washer/disinfectors: recontamination of equipment(SAB(93)32). Department of Health, 1993.

Compatibility of medical devices and their accessories and reprocessingunits with cleaning, disinfecting and sterilizing agents (MDA SN 9619).Medical Devices Agency, Department of Health, 1996.

Decontamination of equipment, linen or other surfaces contaminatedwith hepatitis B and/or human immunodeficiency viruses (H(91)33).Department of Health, 1991.

Health and Safety Executive publications

Control and substances hazardous to health and control of carcinogenicsubstances: Control of substances hazardous to health regulations1988: approved code of practice (L5). 4th edition. Health and SafetyExecutive, HSE Books, 1993.

Manual handling: Manual handling operations regulations 1992:guidance on regulations (L23). Health and Safety Executive, HSE Books,1992.

Occupational exposure limits (EH40). Health and Safety Executive, HSEBooks, issued annually.

Programmable electronic systems in safety related applications: anintroductory guide. Health and Safety Executive, HSE Books, 1987.

Work equipment. Provision and use of work equipment Regulations1992. Guidance on regulations (L22). Health and Safety Executive, HSEBooks, 1992.

Workplace health, safety and welfare. Workplace (Health, Safety andWelfare) Regulations 1992: approved code of practice and guidance(L24). Health and Safety Commission, HSE Books, 1992.

Safety in health service laboratories: safe working and the preventionof infection in clinical laboratories. Health Services AdvisoryCommittee/Health and Safety Executive, HSE Books, 1991.

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References

Safe working and the prevention of infection in the mortuary andpost-mortem room. Health and Safety Executive, TSO, 1991.

British Standards

BS 853 Specification for vessels for use in heating systems.Part 1: 1996 Calorifiers and storage vessels for central heating and hot watersupply.

BS 1449 Steel plate, sheet and strip.Part 2: 1983 Specification for stainless heat resisting steel plate sheet andstrip.

BS 1752: 1983 (1994)Specification for laboratories sintered of fittedfilters including porosity grading.

BS 2745 Washer disinfectors for medical purposes.Part 1: 1993 Specification for general requirements.Part 2: 1993 Specification for human-waste container washer-disinfectors.Part 3: 1993 Specification for washer-disinfectors except those used forprocessing human-waste containers and laundry.

BS 3928: 1969 Method for sodium flame test for air filters (other thanfor air supply to I.C. engines and compressors.

BS 5304: 1988 Code of practice for safety of machinery.

BS 5500: 1997 (1996) Specification for unfired fusion welded pressurevessel.

BS 5728 Measurement of flow of cold potable water in closedconduits.

BS 5726 Microbiological safety cabinets.

BS 7320: 1990 Specification for sharps containers.

BS 7671: 1992 Requirements for electrical installations. IEE WiringRegulations Sixteenth edition.

BS EN 274: 1993 Sanitary tapware. Waste fittings for basins, bidets andbaths. General technical specification.

BS EN 554: 1995 Sterilization of medical devices. Validation and routinecontrol of sterilization by moist heat.

BS EN 556: 1995 Sterilization of medical devices. Requirements forterminally sterilized devices to be labelled. ‘Sterile’.

BS EN 724: 1995 Guidance on the application of EN 29001 and EN46001 and of EN 29002 and EN 46002 for non-active medical devices.

BS EN 46001: 1997 Application of EN ISO 9001 to the manufacture ofmedical devices.

BS EN 46002: 1997 Application of EN ISO 9002 to the manufacture ofmedical devices.

101

References

BS EN ISO 9000 Quality management and quality assurance standards.

BS EN ISO 9001: 1994 Quality systems. Model for quality assurance indesign, development, production, installation and servicing.

BS EN ISO 9002: 1994 Quality systems. Model for quality assurance inproduction, installation and servicing.

EN 2900 Quality systems.

BS EN 50081 Electromagnetic compatibility. Generic emission standard.

BS EN 50081-1: 1992 Residential, commercial and light industry.

BS EN 50081-2: 1994 Industrial environment.

BS EN 50082 Electromagnetic compatibility. Generic immunity standard.

BS EN 50082-1: 1992 Residential, commercial and light industry.

BS EN 50082-2: 1995 Industrial environment.

BS EN 50103: 1996 Guidance on the application of EN 29001 and EN46001 and of EN 29002 and EN 46002 for the active (including activeimplantable) medical service industry.

BS EN 61010 Safety requirements for electrical equipment formeasurement, control and laboratory use.

BS EN 61010-1: 1993 General requirements

BS EN 61010-2-045 (Draft) Particular requirements for washerdisinfectors and other equipment incorporating washing equipment forthe treatment of medical materials and for laboratory processes.

EN (Draft) Washer-disinfectors.Part 1: 1997 (Draft) General requirements and tests.Part 2: 1997 (Draft) Requirements and tests before washer-disinfectors forsurgical instruments and trays, anaesthetic equipment, hollowware andglassware.Part 3: 1997 (Draft) Requirements and tests for washer-disinfectors to human-waste containers.Part 4: 1997 (Provisional) Requirements and tests washer-disinfectors forthermolabile reusable instruments including endoscope.

EN 285 Sterilisation. Steam sterilizers. Large sterilizer.

EN 837 Pressure gauges.Part 1: Board and tubePart 2: Pressure gauges. Selection and installation recommendationsPart 3: Diaphragm and capsule pressure group. Dimension metrology.Requirement testing.

EN 866-1 Biological systems for testing sterilisers. Sterilisationprocesses.Part 1: General requirement

102

References

Other publications

The Building Regulations 1991: approved document B; Fire safety.Department of the Environment and Welsh Office, 1991.

Safe working and the prevention of infection in the mortuary andpost-mortem room. Department of Health, 1991.

Water Supply Bye-laws Guide. 2nd edition, Water Bye-laws AdvisoryService Water Research Centre, 1989.

Babb J. R, Bradley C. R, Barnes A. R. Question and Answer. Journal ofHospital Infection, 1992, vol 20, p51-54.

Rollnick M. How you spend your pennies. Health Estate Journal, May,1991, p12-15.

The rules governing medicinal products in the European Community.Vol IV Good manufacturing practice for medicinal products.Commissions of the European Communities, 1992.

Re-use of medical devices supplied for single use only (MDA DB 9501).Medical Devices Agency, 1995.

Sterilization and disinfection of heat-labile equipment: report of aWorking Party on sterilization and disinfection of heat-labileequipment. Hospital Infection Research Laboratory, 1986.

103

References

About NHS Estates

NHS Estates is an Executive Agency of the Department ofHealth and is involved with all aspects of health estatemanagement, development and maintenance. The Agencyhas a dynamic fund of knowledge which it has acquiredduring over 30 years of working in the field. Using thisknowledge NHS Estates has developed products which areunique in range and depth. These are described below.NHS Estates also makes its experience available to the fieldthrough its consultancy services.

Enquiries about NHS Estates should be addressed to:NHS Estates, Publications Unit, Department of Health, 1 Trevelyan Square, Boar Lane, Leeds LS1 6AE.Telephone 0113 254 7000.http://www.nhsestates.gov.uk

Some NHS Estates products

Activity DataBase – a computerised briefing and designsystem for use in health buildings, applicable to both newbuild and refurbishment schemes. NHS Estates

Design Guides – complementary to Health BuildingNotes, Design Guides provide advice for planners anddesigners about subjects not appropriate to the HealthBuilding Notes series. SO

Estatecode – user manual for managing a health estate.Includes a recommended methodology for propertyappraisal and provides a basis for integration of the estateinto corporate business planning. SO

Concode – outlines proven methods of selecting contractsand commissioning consultants. Reflects official policy oncontract procedures. SO

Works Information Management System – a computerised information system for estatemanagement tasks, enabling tangible assets to be put intothe context of servicing requirements. NHS Estates

Health Building Notes – advice for project teamsprocuring new buildings and adapting or extendingexisting buildings. SO

Health Guidance Notes – an occasional series ofpublications which respond to changes in Department ofHealth policy or reflect changing NHS operationalmanagement. Each deals with a specific topic and iscomplementary to a related HTM. SO

Health Technical Memoranda – guidance on the design,installation and running of specialised building servicesystems, and on specialised building components. SO

Health Facilities Notes – debate current and topicalissues of concern across all areas of healthcare provision.SO

Encode – shows how to plan and implement a policy ofenergy efficiency in a building. SO

Firecode – for policy, technical guidance and specialistaspects of fire precautions. SO

Capital Investment Manual Database – softwaresupport for managing the capital programme. Compatiblewith Capital Investment Manual. NHS Estates

Model Engineering Specifications – comprehensiveadvice used in briefing consultants, contractors andsuppliers of healthcare engineering services to meetDepartmental policy and best practice guidance. NHS Estates

Quarterly Briefing – gives a regular overview on theconstruction industry and an outlook on how this mayaffect building projects in the health sector, in particularthe impact on business prices. Also provides informationon new and revised cost allowances for health buildings.Published four times a year; available on subscriptiondirect from NHS Estates. NHS Estates

Items noted “SO” can be purchased from The StationeryOffice Bookshops in London (post orders to PO Box 276,SW8 5DT), Edinburgh, Belfast, Manchester, Birminghamand Bristol or through good booksellers.

NHS Estates consultancy service

Designed to meet a range of needs from advice on theoversight of estates management functions to a muchfuller collaboration for particularly innovative or exemplaryprojects.

Enquiries should be addressed to: NHS Estates ConsultancyService (address as above).

www.nhsestates.gov.uk

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